schemas: add missing vim modeline

Similar to f7160f32 "schemas: Add vim modeline"
Signed-off-by: NVictor Toso <victortoso@redhat.com>
Message-Id: <20211220145624.52801-1-victortoso@redhat.com>
Acked-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

qapi/audio.json

 # -*- mode: python -*-
+# vim: filetype=python
 #
 # Copyright (C) 2015-2019 Zoltán Kővágó <DirtY.iCE.hu@gmail.com>
 #

qapi/compat.json

 # -*- Mode: Python -*-
+# vim: filetype=python
 
 ##
 # = Compatibility policy

qapi/replay.json

 # -*- Mode: Python -*-
+# vim: filetype=python
 #
 
 ##

qapi/trace.json

 # -*- mode: python -*-
+# vim: filetype=python
 #
 # Copyright (C) 2011-2016 Lluís Vilanova <vilanova@ac.upc.edu>
 #