tests/sh_match.sh: redirect ulimit to 2>/dev/null

macOS 12.2.1 doesn't seem to like the -M, -v or -d ulimit options:

  sh_match.sh[502]: FAIL: test_xmlfragment1/0/testfile1.xml:
  Expected empty stderr, got $'test1_script.sh[2]: ulimit: 1048576:
  limit exceeded [Invalid argument]\ntest1_script.sh[3]: ulimit:
  1048576: limit exceeded [Invalid argument]\ntest1_script.sh[4]:
  ulimit: 1048576: limit exceeded [Invalid argument]'

The 'Invalid argument' addition is caused by errno==EINVAL and
suggests the OS either doesn't support setting this limit, or
support for it was somehow disabled.

src/cmd/ksh93/tests/sh_match.sh:
- Redirect standard error for ulimit commands to 2>/dev/null. If
  they fail it's pretty inconsequential and it's not related to
  actual ${.sh.match} testing at all.

Resolves: https://github.com/ksh93/ksh/issues/459
Thanks to @posguy99 for the report.

src/cmd/ksh93/tests/sh_match.sh

@@ -130,9 +130,11 @@ function test_xmlfragment1
 	typeset -r testscript='test1_script.sh'
 cat >"${testscript}" <<-TEST1SCRIPT
 	# memory safeguards to prevent out-of-control memory consumption
-	ulimit -M \$(( 1024 * 1024 ))
-	ulimit -v \$(( 1024 * 1024 ))
-	ulimit -d \$(( 1024 * 1024 ))
+	{
+		ulimit -M \$(( 1024 * 1024 ))
+		ulimit -v \$(( 1024 * 1024 ))
+		ulimit -d \$(( 1024 * 1024 ))
+	} 2>/dev/null
 
 	# input text
 	xmltext="\$( < "\$1" )"
@@ -149,7 +151,7 @@ cat >"${testscript}" <<-TEST1SCRIPT
 		nameref ar="\$1"
 
 		# fixme:
-		# - We want to enforce standard conformance - does ~(Exp) or ~(Ex-p) does that ?
+		# - We want to enforce standard conformance - does ~(Exp) or ~(Ex-p) do that ?
 		dummy="\${xmltext//~(Ex-p)(?:
 			(<!--.*-->)+?|			# xml comments
 			(<[:_[:alnum:]-]+