app-data: Expand release entry
This makes the appdata check pass with 0.7.14 and 0.7.15, otherwise it fails like:
2/3 Validate appstream file FAIL 0.14 s (exit status 1)
--- command ---
/usr/bin/appstream-util validate --nonet data/sm.puri.Chatty.appdata.xml
--- stdout ---
data/sm.puri.Chatty.appdata.xml: FAILED:
• style-invalid : <p> does not end in '.|:|!' [Development release]
• style-invalid : <p> is too short [Development release]
--- stderr ---