stripspace: call U+0020 a "space" instead of a "blank"

I couldn't find any other examples of people referring to this
character as a "blank".

Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/stripspace.c

@@ -35,7 +35,7 @@ int cmd_stripspace(int argc, const char **argv, const char *prefix)
 			    N_("skip and remove all lines starting with comment character"),
 			    STRIP_COMMENTS),
 		OPT_CMDMODE('c', "comment-lines", &mode,
-			    N_("prepend comment character and blank to each line"),
+			    N_("prepend comment character and space to each line"),
 			    COMMENT_LINES),
 		OPT_END()
 	};