patch 9.0.1966: configure prints stray 6 when checking libruby

Problem:  configure prints stray 6 when checking libruby
Solution: redirect stdout to dev/null

configure: Do not print "6" when checking for libruby

`expr` will print the matched string length to the standard output.
Current `configure` output looks like this:

```
checking Ruby header files...  /usr/include/ruby-3.1.0
6
```

The script really only cares about `expr` exit code.

closes: #13234

Signed-off-by: Christian Brabandt <[email protected]>
Co-authored-by: Illia Bobyr <[email protected]>

Author: illia-bobyr

src/auto/configure

@@ -8102,7 +8102,7 @@ printf "%s\n" "$rubyhdrdir" >&6; }
 	librubyarg=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['LIBRUBYARG'])"`
 	librubya=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['LIBRUBY_A'])"`
 	rubylibdir=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG['libdir'])"`
-	if test -f "$rubylibdir/$librubya" || expr "$librubyarg" : "-lruby"; then
+	if test -f "$rubylibdir/$librubya" || expr "$librubyarg" : "-lruby" >/dev/null; then
 	  RUBY_LIBS="$RUBY_LIBS -L$rubylibdir"
 	elif test "$librubyarg" = "libruby.a"; then
 	  	  librubyarg="-lruby"

src/configure.ac

@@ -2077,7 +2077,7 @@ if test "$enable_rubyinterp" = "yes" -o "$enable_rubyinterp" = "dynamic"; then
 	librubyarg=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG[['LIBRUBYARG']])"`
 	librubya=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG[['LIBRUBY_A']])"`
 	rubylibdir=`$vi_cv_path_ruby -r rbconfig -e "print $ruby_rbconfig.expand($ruby_rbconfig::CONFIG[['libdir']])"`
-	if test -f "$rubylibdir/$librubya" || expr "$librubyarg" : "-lruby"; then
+	if test -f "$rubylibdir/$librubya" || expr "$librubyarg" : "-lruby" >/dev/null; then
 	  RUBY_LIBS="$RUBY_LIBS -L$rubylibdir"
 	elif test "$librubyarg" = "libruby.a"; then
 	  dnl required on Mac OS 10.3 where libruby.a doesn't exist

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1966,
 /**/
     1965,
 /**/