t9132-git-svn-broken-symlink.sh: use the $( ... ) construct for command substitution

The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
	perl -i -pe 'BEGIN{undef $/;} s/`(.+?)`/\$(\1)/smg'  "${_f}"
done

and then carefully proof-read.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9132-git-svn-broken-symlink.sh

@@ -87,7 +87,7 @@ test_expect_success 'clone using git svn' 'git svn clone -r1 "$svnrepo" x'
 
 test_expect_success SYMLINKS '"bar" is a symlink that points to "asdf"' '
 	test -L x/bar &&
-	(cd x && test xasdf = x"`git cat-file blob HEAD:bar`")
+	(cd x && test xasdf = x"$(git cat-file blob HEAD:bar)")
 '
 
 test_expect_success 'get "bar" => symlink fix from svn' '
@@ -96,7 +96,7 @@ test_expect_success 'get "bar" => symlink fix from svn' '
 
 test_expect_success SYMLINKS '"bar" remains a proper symlink' '
 	test -L x/bar &&
-	(cd x && test xdoink = x"`git cat-file blob HEAD:bar`")
+	(cd x && test xdoink = x"$(git cat-file blob HEAD:bar)")
 '
 
 test_done