send-email: remove stray characters from usage

A few stray single quotes crept into the usage string in a2ce608
(send-email docs: add format-patch options, 2021-10-25).  Remove them.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: tmzullinger

git-send-email.perl

@@ -28,8 +28,8 @@
 
 sub usage {
 	print <<EOT;
-git send-email' [<options>] <file|directory>
-git send-email' [<options>] <format-patch options>
+git send-email [<options>] <file|directory>
+git send-email [<options>] <format-patch options>
 git send-email --dump-aliases
 
   Composing: