[SPARK-46972][SQL][TESTS][FOLLOWUP] Remove the assertion for table ex…

…istence

### What changes were proposed in this pull request?

This PR removes the assertion for table existence, which introduces undefined scan logic.

### Why are the changes needed?

test improvement

### Does this PR introduce _any_ user-facing change?

no
### How was this patch tested?

the existing one

### Was this patch authored or co-authored using generative AI tooling?
no

Closes #45163 from yaooqinn/SPARK-46972-F.

Authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Kent Yao <yao@apache.org>

sql/core/src/test/scala/org/apache/spark/sql/connector/DataSourceV2SQLSuite.scala

@@ -1740,7 +1740,6 @@ class DataSourceV2SQLSuiteV1Filter
     spark.conf.unset(V2_SESSION_CATALOG_IMPLEMENTATION.key)
     withTable("t") {
       sql(s"CREATE TABLE t(c char(1), v varchar(2)) USING $v2Source")
-      assert(!spark.table("t").isEmpty)
     }
   }