[omemo] Update CHANGELOG & manifest.ini

omemo/CHANGELOG

+2.7.8 / 2020-09-12
+- Remove not needed code
+
 2.7.7 / 2020-06-28
 - Add hints for the fingerprint dialog
 

omemo/manifest.ini

 [info]
 name: OMEMO
 short_name: omemo
-version: 2.7.7
+version: 2.7.8
 description: OMEMO is an XMPP Extension Protocol (XEP) for secure multi-client end-to-end encryption based on Axolotl and PEP. You need to install some dependencies, detailed in the installation instructions for your system in the GitLab wiki.
 authors: Bahtiar `kalkin-` Gadimov <bahtiar@gadimov.de>
  Daniel Gultsch <daniel@gultsch.de>