[REF] Clean oca_dependencies.txt, bye dev branches

Dev branches were closed
12.0-mig-base_external_dbsource_mysql
https://github.com/OCA/server-backend/pull/22
https://github.com/OCA/server-backend/pull/84

12.0-mig-base_external_dbsource_sqlite
https://github.com/OCA/server-backend/pull/21
https://github.com/OCA/server-backend/pull/58

oca_dependencies.txt

@@ -1,7 +1,4 @@
 server-tools
-server-backend https://github.com/OCA/server-backend
+server-backend
 web
 queue
-# Until merge
-server-backend-mig-dbsource-sqlite https://github.com/Eficent/server-backend 12.0-mig-base_external_dbsource_sqlite
-server-backend-mig-dbsource-mysql https://github.com/Eficent/server-backend 12.0-mig-base_external_dbsource_mysql