FLINK-36479 Remove deprecated method Table getSchema as

[jbalchan]

What is the purpose of the change

https://issues.apache.org/jira/browse/FLINK-36479 Remove deprecated methods Table#getSchema and Table#as

Brief change log

Remove deprecated methods

Verifying this change

This change is already covered by existing tests

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 1a0e5c8 Azure: FAILURE

Bot commands

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• @flinkbot run azure re-run the last Azure build

[jbalchan]

i'm sorry. I was trying to remove my commit which failed the jenkins check. But PR itself got closed.