fix: application settings marshalling

What
---
Update `Settings.PerformanceBarAllowedGroupID` to be an `int` instead
`string`

Why
---
The API returns an int because it's a group ID:

```
curl -s --header "PRIVATE-TOKEN: TOKEN" "https://gitlab.example.com/api/v4/application/settings" | jq -r '.performance_bar_allowed_group_id'
1234
```

The
[documentation](https://gitlab.com/gitlab-org/gitlab/-/blob/784401ac8b5bf5ae3056cc84a95fb2be37c83934/doc/api/settings.md#L92)
specifies that it's an `int`, and it's also stored as an int in the
[database](https://gitlab.com/gitlab-org/gitlab/-/blob/784401ac8b5bf5ae3056cc84a95fb2be37c83934/db/structure.sql#L11472).

Signed-off-by: Steve Xuereb <sxuereb@gitlab.com>

settings.go

@@ -238,7 +238,7 @@ type Settings struct {
 	PasswordSymbolRequired                                bool              `json:"password_symbol_required"`
 	PasswordUppercaseRequired                             bool              `json:"password_uppercase_required"`
 	PasswordLowercaseRequired                             bool              `json:"password_lowercase_required"`
-	PerformanceBarAllowedGroupID                          string            `json:"performance_bar_allowed_group_id"`
+	PerformanceBarAllowedGroupID                          int               `json:"performance_bar_allowed_group_id"`
 	PerformanceBarAllowedGroupPath                        string            `json:"performance_bar_allowed_group_path"`
 	PerformanceBarEnabled                                 bool              `json:"performance_bar_enabled"`
 	PersonalAccessTokenPrefix                             string            `json:"personal_access_token_prefix"`
@@ -617,7 +617,7 @@ type UpdateSettingsOptions struct {
 	PasswordSymbolRequired                                *bool              `url:"password_symbol_required,omitempty" json:"password_symbol_required,omitempty"`
 	PasswordUppercaseRequired                             *bool              `url:"password_uppercase_required,omitempty" json:"password_uppercase_required,omitempty"`
 	PasswordLowercaseRequired                             *bool              `url:"password_lowercase_required,omitempty" json:"password_lowercase_required,omitempty"`
-	PerformanceBarAllowedGroupID                          *string            `url:"performance_bar_allowed_group_id,omitempty" json:"performance_bar_allowed_group_id,omitempty"`
+	PerformanceBarAllowedGroupID                          *int               `url:"performance_bar_allowed_group_id,omitempty" json:"performance_bar_allowed_group_id,omitempty"`
 	PerformanceBarAllowedGroupPath                        *string            `url:"performance_bar_allowed_group_path,omitempty" json:"performance_bar_allowed_group_path,omitempty"`
 	PerformanceBarEnabled                                 *bool              `url:"performance_bar_enabled,omitempty" json:"performance_bar_enabled,omitempty"`
 	PersonalAccessTokenPrefix                             *string            `url:"personal_access_token_prefix,omitempty" json:"personal_access_token_prefix,omitempty"`