psuh: fix SYNOPSIS to use space instead of hyphen

The adoc SYNOPSIS had 'git-psuh' (hyphen) but the -h output from
psuh_usage[] produces 'git psuh' (space), causing t0450 to fail.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nhlong9697

Documentation/git-psuh.adoc

@@ -9,7 +9,7 @@ git-psuh - Delight users' typo with a shy horse
 SYNOPSIS
 --------
 [verse]
-'git-psuh [<arg>...]'
+'git psuh [<arg>...]'
 
 DESCRIPTION
 -----------