po: Add missing files to POTFILES.in

These files were adding translatable texts.

po/POTFILES.in

@@ -1,5 +1,6 @@
 data/org.gnome.Calls.desktop.in
 data/org.gnome.Calls-daemon.desktop.in
+plugins/sip/sip-account-widget.ui
 src/calls-application.c
 src/calls-best-match.c
 src/calls-call.c
@@ -24,6 +25,7 @@ src/calls-provider.c
 src/calls-record-store.c
 src/calls-ringer.c
 src/main.c
+src/ui/account-overview.ui
 src/ui/call-display.ui
 src/ui/call-record-row.ui
 src/ui/call-selector-item.ui