maint: Grammar fix to mailmap

Make the sentence read better.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20181207170733.129532-1-eblake@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

.mailmap

@@ -34,6 +34,6 @@ Justin Terry (VM) <juterry@microsoft.com> Justin Terry (VM) via Qemu-devel <qemu
 
 
 # Also list preferred name forms where people have changed their
-# git author config, or having utf8/latin1 encoding issues.
+# git author config, or had utf8/latin1 encoding issues.
 Daniel P. Berrangé <berrange@redhat.com>
 Reimar Döffinger <Reimar.Doeffinger@gmx.de>