brew.sh: fix brew -v

`brew -v` was previously equivalent to `brew --version`, but it
currently returns the output of `brew help`. (This also occurs with
`brew -x`, where x is any single character.)

This is because the `-?` pattern matches `-` followed by any single
character. We need to quote it to capture the intended meaning.

Library/Homebrew/brew.sh

@@ -166,7 +166,7 @@ case "$@" in
     homebrew-list "$@" && exit 0
     ;;
   # falls back to cmd/help.rb on a non-zero return
-  help | --help | -h | --usage | -? | "")
+  help | --help | -h | --usage | "-?" | "")
     homebrew-help "$@" && exit 0
     ;;
 esac