[SPARK-49078][SQL][FOLLOWUP] Clear unused showColumnsNotSupportedForV…

…2TablesError in QueryCompilationErrors and add more uts

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

Clear unused error methods in QueryCompilationErrors.

### Why are the changes needed?

Due to had support show columns in v2 table(apache#47568), so the check method is not needed any more.

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

No

### How was this patch tested?

not need

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

Closes apache#47701 from xuzifu666/rm_showcolumnsv2.

Lead-authored-by: xuyu <11161569@vivo.com>
Co-authored-by: xuzifu666 <1206332514@qq.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

sql/catalyst/src/main/scala/org/apache/spark/sql/errors/QueryCompilationErrors.scala

@@ -1593,10 +1593,6 @@ private[sql] object QueryCompilationErrors extends QueryErrorsBase with Compilat
     notSupportedForV2TablesError("SHOW CREATE TABLE AS SERDE")
   }
 
-  def showColumnsNotSupportedForV2TablesError(): Throwable = {
-    notSupportedForV2TablesError("SHOW COLUMNS")
-  }
-
   def repairTableNotSupportedForV2TablesError(): Throwable = {
     notSupportedForV2TablesError("MSCK REPAIR TABLE")
   }

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

@@ -2374,6 +2374,8 @@ class DataSourceV2SQLSuiteV1Filter
     val t = "testcat.ns1.ns2.tbl"
     withTable(t) {
       spark.sql(s"CREATE TABLE $t (id bigint, data string) USING foo")
+      checkAnswer(sql(s"SHOW COLUMNS FROM $t IN testcat.ns1.ns2"), Seq(Row("id"), Row("data")))
+      checkAnswer(sql(s"SHOW COLUMNS in $t"), Seq(Row("id"), Row("data")))
       checkAnswer(sql(s"SHOW COLUMNS FROM $t"), Seq(Row("id"), Row("data")))
     }
   }