update codeowners so that each file at least assigns the core team

CODEOWNERS

@@ -1,6 +1,10 @@
 # Each line is a file pattern followed by one or more owners.
 # More on CODEOWNERS files: https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners
 
+# The rules are evaluated in order, if a file matches multiple patterns, the last match "wins".
+# We want to have a default rule for all files
+* @hashicorp/terraform-core
+
 # Entries that are commented out have maintainers that are not in the
 # HashiCorp organization and so cannot be automatically added as reviewers.
 #
@@ -24,12 +28,3 @@ builtin/provisioners/file               @hashicorp/terraform-core
 builtin/provisioners/local-exec         @hashicorp/terraform-core
 builtin/provisioners/remote-exec        @hashicorp/terraform-core
 
-# go.sum files should never cause automatic review requests because they only
-# ever change in response to go.mod files (our PR checks would fail if not) and
-# if a specific module has _only_ a go.sum update without an associated go.mod
-# update then that represents that the update cannot affect the module, and
-# the Go toolchain just needed to download something new to prove that.
-#
-# (The last match in the file "wins", so this overrides any explicit owner
-# specified above when go.sum is the only file that changed.)
-*/go.sum   # no owner for these