shellcheck: avoid unnecessary echo

Shellcheck advises:

  SC2005: Useless echo? Instead of 'echo $(cmd)', just use 'cmd'.

The extra echo was added in 9bd52f as a workaround for `wc' in OSX,
which printed extra whitespace before the character count. Fix this
issue in a different way by piping the `wc' output through `awk'.

This also means that we no longer use the suggested workaround, so
remove the dangling acknowledgement.

README.md

@@ -46,6 +46,3 @@ The script is licensed under the
 
 I didn't invent the wheel, just packaged it nicely. All credits go to the
 [Ghostscript](http://www.ghostscript.com) team.
-
-Many thanks to Dr. Alun J. Carr for fixing a portability issue on Mac OS X
-regarding leading whitespace in the output of `wc`.

shrinkpdf.sh

@@ -57,8 +57,8 @@ check_smaller ()
 	if [ ! -f "$1" ] || [ ! -f "$2" ]; then
 		return 0;
 	fi
-	ISIZE="$(echo $(wc -c "$1") | cut -f1 -d\ )"
-	OSIZE="$(echo $(wc -c "$2") | cut -f1 -d\ )"
+	ISIZE="$(wc -c "$1" | awk '{ print $1 }')"
+	OSIZE="$(wc -c "$2" | awk '{ print $1 }')"
 	if [ "$ISIZE" -lt "$OSIZE" ]; then
 		echo "Input smaller than output, doing straight copy" >&2
 		cp "$1" "$2"