t1050-large.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
   sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
done

and then carefully proof-read.

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

t/t1050-large.sh

@@ -131,7 +131,7 @@ test_expect_success 'git-show a large file' '
 '
 
 test_expect_success 'index-pack' '
-	git clone file://"`pwd`"/.git foo &&
+	git clone file://"$(pwd)"/.git foo &&
 	GIT_DIR=non-existent git index-pack --strict --verify foo/.git/objects/pack/*.pack
 '
 
@@ -140,7 +140,7 @@ test_expect_success 'repack' '
 '
 
 test_expect_success 'pack-objects with large loose object' '
-	SHA1=`git hash-object huge` &&
+	SHA1=$(git hash-object huge) &&
 	test_create_repo loose &&
 	echo $SHA1 | git pack-objects --stdout |
 		GIT_ALLOC_LIMIT=0 GIT_DIR=loose/.git git unpack-objects &&