[SPARK-52875][SQL][TESTS][FOLLOWUP] Override the sparkConf for DataSourceV2StrategySuite to ensure that ANSI_ENABLED is set to true.

[LuciferYang]

What changes were proposed in this pull request?

This pr ensures that the test case Partial constant folding of math functions in DataSourceV2StrategySuite is only run when ansiEnabled is set to true.

Why are the changes needed?

Restore Non-Ansi daily test:

• https://github.com/apache/spark/actions/runs/16485653304/job/46609769023

Does this PR introduce any user-facing change?

No

How was this patch tested?

SPARK_ANSI_SQL_MODE=false build/sbt "sql/testOnly org.apache.spark.sql.execution.datasources.v2.DataSourceV2StrategySuite"
[info] Run completed in 1 second, 939 milliseconds.
[info] Total number of tests run: 11
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 11, failed 0, canceled 1, ignored 0, pending 0
[info] All tests passed.

Was this patch authored or co-authored using generative AI tooling?

No

[LuciferYang]

It seems that checkV2Conversion cannot use the withSQLConf method to enforce ansiEnabled to be true, so an assume statement has been added here instead. Do you think this approach is acceptable? @cloud-fan

spark/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2StrategySuite.scala

Lines 838 to 846 in 4dc4260

	private def checkV2Conversion(
	catalystExpr: Expression,
	v2Expr: V2Expression,
	isPredicate: Boolean = false): Unit = {
	val v2ExprActual = new V2ExpressionBuilder(catalystExpr, isPredicate).build().getOrElse {
	fail(s"can't convert to V2 expression: $catalystExpr")
	}
	assert(v2ExprActual == v2Expr, "V2 expressions must match")
	}

[cloud-fan]

can we override def sparkConf to enable ansi for the entire suite? DS v2 needs to turn on ANSI to translate expressions.

[LuciferYang]

Close this PR because it has already been fixed in #51660.