sync warning settings

_CoqProject

 -Q theories reloc
 # We sometimes want to locally override notation, and there is no good way to do that with scopes.
 -arg -w -arg -notation-overridden
-# change_no_check does not exist yet in 8.9.
--arg -w -arg -convert_concl_no_check
-# non-canonical projections (https://github.com/coq/coq/pull/10076) do not exist yet in 8.9.
+# Cannot use non-canonical projections as it causes massive unification failures
+# (https://github.com/coq/coq/issues/6294).
 -arg -w -arg -redundant-canonical-projection
-# "Declare Scope" does not exist yet in 8.9.
--arg -w -arg -undeclared-scope
-# We have ambiguous paths and so far it is not even clear what they are (https://gitlab.mpi-sws.org/iris/iris/issues/240).
--arg -w -arg -ambiguous-paths
 
 theories/prelude/ctx_subst.v
 theories/prelude/properness.v