Fix the example of a plugin info file in docs.
Fix the example of a plugin info file in docs.

The header has changed from [YourApp Plugin] to [Plugin].

Distrotech/libpeas,chergert/libpeas,GNOME/libpeas,chergert/libpeas,Distrotech/libpeas,gregier/libpeas,gregier/libpeas,gregier/libpeas,GNOME/libpeas,gregier/libpeas,chergert/libpeas,Distrotech/libpeas