MSVC: Remove duplicate PATH entry in test harness.

Back-patch to 9.5, where commit 4cb7d671fd
introduced it.

src/tools/msvc/vcregress.pl

@@ -50,7 +50,7 @@ copy("$Config/autoinc/autoinc.dll",               "src/test/regress");
 copy("$Config/regress/regress.dll",               "src/test/regress");
 copy("$Config/dummy_seclabel/dummy_seclabel.dll", "src/test/regress");
 
-$ENV{PATH} = "$topdir/$Config/libpq;$topdir/$Config/libpq;$ENV{PATH}";
+$ENV{PATH} = "$topdir/$Config/libpq;$ENV{PATH}";
 
 my $schedule = shift;
 unless ($schedule)