Documentation/glossary: fix double word

Remove a spurious "that".

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Martin Ågren

Documentation/glossary-content.txt

@@ -550,7 +550,7 @@ The following pseudorefs are known to Git:
 	to the result.
 
 [[def_ref]]ref::
-	A name that that points to an <<def_object_name,object name>> or
+	A name that points to an <<def_object_name,object name>> or
 	another ref (the latter is called a <<def_symref,symbolic ref>>).
 	For convenience, a ref can sometimes be abbreviated when used
 	as an argument to a Git command; see linkgit:gitrevisions[7]