Fix various typo errors in code comments across multiple modules

[ycli12]

What changes were proposed?

Fix several typo errors found in code comments across multiple modules:

• neccessary → necessary in WriteToStreamStatement.scala
• overriden → overridden in Client.scala and V2JDBCTest.scala
• custome → custom in TaskSetManager.scala
• commiting → committing in StreamRealTimeModeSuite.scala
• curent → current in RocksDBStateStoreSuite.scala
• commited → committed in StateStoreSuite.scala

Why are the changes needed?

To improve code readability and maintain consistency in documentation. Typos in comments can mislead contributors unfamiliar with the codebase.

Does this PR introduce any user-facing change?

No. This is a documentation-only change in code comments.