chore!: enable gapicv2 for monitoring/v3 API

This introduces the following breakages upon code regeneration, which are due to the `TimeSeriesQueryLanguageCondition` type being removed from `alert.proto` in a preceding change.

```
[ERROR] 6011: com.google.monitoring.v3.AlertPolicy$Condition: Field CONDITION_TIME_SERIES_QUERY_LANGUAGE_FIELD_NUMBER has been removed, but it was previously a constant
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition getConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageConditionOrBuilder getConditionTimeSeriesQueryLanguageOrBuilder()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition: Method 'public boolean hasConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$Builder clearConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition getConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition$Builder getConditionTimeSeriesQueryLanguageBuilder()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageConditionOrBuilder getConditionTimeSeriesQueryLanguageOrBuilder()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public boolean hasConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$Builder mergeConditionTimeSeriesQueryLanguage(com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition)' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$Builder setConditionTimeSeriesQueryLanguage(com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition)' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$Condition$Builder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$Builder setConditionTimeSeriesQueryLanguage(com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition$Builder)' has been removed
[ERROR] 6001: com.google.monitoring.v3.AlertPolicy$Condition$ConditionCase: Removed field CONDITION_TIME_SERIES_QUERY_LANGUAGE
[ERROR] 8001: com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition: Class com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition removed
[ERROR] 8001: com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition$Builder: Class com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition$Builder removed
[ERROR] 8001: com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageConditionOrBuilder: Class com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageConditionOrBuilder removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$ConditionOrBuilder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageCondition getConditionTimeSeriesQueryLanguage()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$ConditionOrBuilder: Method 'public com.google.monitoring.v3.AlertPolicy$Condition$TimeSeriesQueryLanguageConditionOrBuilder getConditionTimeSeriesQueryLanguageOrBuilder()' has been removed
[ERROR] 7002: com.google.monitoring.v3.AlertPolicy$ConditionOrBuilder: Method 'public boolean hasConditionTimeSeriesQueryLanguage()' has been removed
```

Committer: @miraleung
PiperOrigin-RevId: 311581003