doc/ext: fix stray whitespace
doc/ext: fix stray whitespace

Introduced by changes in #998.

git/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,mosoft521/gitscm-next,jasonlong/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,jasonlong/git-scm.com,jasonlong/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,git/git-scm.com,jasonlong/git-scm.com,mosoft521/gitscm-next