rtp: fix g-i warnings

Use same variable name in function declaration as in function
definition and gtk-doc/g-i blurb.
6 jobs for rtp-meta-fix-gi-warnings in 30 minutes and 12 seconds (queued for 3 minutes and 5 seconds)
Status Job ID Name Coverage
  Preparation
passed gst indent #64750

00:00:36

passed manifest #64749

00:00:23

 
  Build
passed build fedora x86_64 #64751

00:03:44

 
  Test
passed check fedora #64752

00:15:47

 
  Full Builds
passed build android arm64 api28 #64753

00:03:03

passed build cerbero fedora x86_64 #64754

00:09:39