Treat translations plugin as any other OP plugin

Replace special handling with simple entry point in
openproject-translations plugin.
See https://github.com/opf/openproject-translations/commit/4fe08c6e646a598e2e055ba7c7b4b938a3a9516b

Bug # 14679

Signed-off-by: Alex Coles <alex@alexbcoles.com>