Fennec F-Droid: switch to the ESR 68 repository

Fennec now lives there. See

    https://docs.google.com/document/d/1oRPkwP3l7QzdQYj0Wn7d_3EfTZaakocA_i_pGKlG0dI/edit

metadata/org.mozilla.fennec_fdroid.yml

@@ -6,7 +6,7 @@ Categories:
   - Internet
 License: MPL-2.0
 WebSite: https://wiki.mozilla.org/Mobile/Platforms/Android#System_Requirements
-SourceCode: http://hg.mozilla.org
+SourceCode: https://hg.mozilla.org/releases/mozilla-esr68/
 IssueTracker: https://bugzilla.mozilla.org
 Changelog: https://www.mozilla.org/en-US/firefox/android/notes/
 Donate: https://sendto.mozilla.org/page/contribute/openwebfund
@@ -22,7 +22,7 @@ Description: |-
     anytime.
 
 RepoType: hg
-Repo: https://hg.mozilla.org/releases/mozilla-release/
+Repo: https://hg.mozilla.org/releases/mozilla-esr68/
 
 Builds:
   - versionName: '35.0'