[enh] put branch name inside backtick

@Morganov has suggested to put branch name inside backtick[1].

[1]: progit#1445 (comment)

Author: Vipul Kumar

book/09-git-and-other-scms/sections/client-bzr.asc

@@ -129,7 +129,7 @@ Git's remote-helpers framework has some limitations that apply.
 In particular, these commands don't work:
 
 * git push origin :branch-to-delete (Bazaar can't accept ref deletions in this way)
-* git push origin old:new (it will push 'old')
+* git push origin old:new (it will push `old`)
 * git push --dry-run origin branch (it will push)
 
 ===== Summary