examples: fix warnings on example-tmdb

All -Wdeclaration-after-statement such as:

 warning: ISO C90 forbids mixed declarations and code
 const gchar *title = grl_media_get_title (media);
 ^~~~~

https://bugzilla.gnome.org/show_bug.cgi?id=768557
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Status Job ID Name Coverage
  Test
passed #212935
build_stable

00:11:29