Add missing comma in Permissions-Policy

This adds a missing comma in the Permissions-Policy response header value.

Tested: no; I didn't even try to compile it.

Change-Id: I4f08b54a5e5af040e10a95d913ef8b457f5bd457
Signed-off-by: Joseph Reynolds <joseph-reynolds@charter.net>
diff --git a/include/security_headers.hpp b/include/security_headers.hpp
index 9615f65..1b9e984 100644
--- a/include/security_headers.hpp
+++ b/include/security_headers.hpp
@@ -48,7 +48,7 @@
                                         "payment=(),"
                                         "picture-in-picture=(),"
                                         "publickey-credentials-get=(),"
-                                        "speaker-selection=()"
+                                        "speaker-selection=(),"
                                         "sync-xhr=(self),"
                                         "unoptimized-images=(self),"
                                         "unsized-media=(self),"