### What changes were proposed in this pull request?
This PR aims to clean up `InMemoryRelation.ser` in `CachedBatchSerializerSuite`.
### Why are the changes needed?
SPARK-32274 makes SQL cache serialization pluggable.
```
[SPARK-32274][SQL] Make SQL cache serialization pluggable
```
This causes UT failures.
```
$ build/sbt "sql/testOnly *.CachedBatchSerializerSuite *.CachedTableSuite"
...
[info] Cause: java.lang.IllegalStateException: This does not work. This is only for testing
[info] at org.apache.spark.sql.execution.columnar.TestSingleIntColumnarCachedBatchSerializer.convertInternalRowToCachedBatch(CachedBatchSerializerSuite.scala:49)
...
[info] *** 30 TESTS FAILED ***
[error] Failed: Total 51, Failed 30, Errors 0, Passed 21
[error] Failed tests:
[error] org.apache.spark.sql.CachedTableSuite
[error] (sql/test:testOnly) sbt.TestsFailedException: Tests unsuccessful
```
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Manually.
```
$ build/sbt "sql/testOnly *.CachedBatchSerializerSuite *.CachedTableSuite"
[info] Tests: succeeded 51, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[info] Passed: Total 51, Failed 0, Errors 0, Passed 51
```
Closes#29346 from dongjoon-hyun/SPARK-32524-3.
Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
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