Remove the 'ca-references' feature check

Fixes #3422.
Fixes #4425.

src/libstore/local-store.cc

@@ -1244,11 +1244,6 @@ void LocalStore::addToStore(const ValidPathInfo & info, Source & source,
 
             deletePath(realPath);
 
-            // text hashing has long been allowed to have non-self-references because it is used for drv files.
-            bool refersToSelf = info.references.count(info.path) > 0;
-            if (info.ca.has_value() && !info.references.empty() && !(std::holds_alternative<TextHash>(*info.ca) && !refersToSelf))
-                settings.requireExperimentalFeature("ca-references");
-
             /* While restoring the path from the NAR, compute the hash
                of the NAR. */
             HashSink hashSink(htSHA256);