Cleanup perl code from unused variables and routines

This commit removes unused variables and routines from some perl code
that have accumulated across the years.  This touches the following
areas:
- Wait event generation script.
- AdjustUpgrade.pm.
- TAP perl code

Author: Alexander Lakhin
Reviewed-by: Dagfinn Ilmari Mannsåker
Discussion: https://postgr.es/m/70b340bc-244a-589d-ef8b-d8aebb707a84@gmail.com

src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm

@@ -534,7 +534,6 @@ sub _mash_view_qualifiers
 		{
 			my @thischunks = split /;/, $chunk, 2;
 			my $stmt = shift(@thischunks);
-			my $ostmt = $stmt;
 
 			# now $stmt is just the body of the CREATE [MATERIALIZED] VIEW
 			$stmt =~ s/$qualifier\.//g;