[Spark] Remove two unused methods in DeltaErrors.scala

- [X] Spark
- [ ] Standalone
- [ ] Flink
- [ ] Kernel
- [ ] Other (fill in here)

Remove two unused methods in DeltaErrors.scala

N/A

Closes delta-io#2309

GitOrigin-RevId: 55d8b064ff70c4d4b9a0410559ab3faac33ae801

spark/src/main/scala/org/apache/spark/sql/delta/DeltaErrors.scala

@@ -2910,14 +2910,6 @@ trait DeltaErrorsBase
       pos = 0)
   }
 
-  def deletionVectorNonIncrementalUpdate(): Throwable = {
-    new DeltaIllegalStateException(errorClass = "DELTA_DELETION_VECTOR_NON_INCREMENTAL_UPDATE")
-  }
-
-  def deletionVectorOverlappingRows(): Throwable = {
-    new DeltaIllegalStateException(errorClass = "DELTA_DELETION_VECTOR_OVERLAPPING_ROWS")
-  }
-
   def statsRecomputeNotSupportedOnDvTables(): Throwable = {
     new DeltaCommandUnsupportedWithDeletionVectorsException(
       errorClass = "DELTA_UNSUPPORTED_STATS_RECOMPUTE_WITH_DELETION_VECTORS",