user-manual: Fix 'you - Git' -> 'you--Git' typo
user-manual: Fix 'you - Git' -> 'you--Git' typo

Use an em-dash, not a hyphen, to join these clauses.

Signed-off-by: W. Trevor King <f75897670c17327c42ab201733fb8a81ff9f4c34@tremily.us>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git