Revert "XFAIL test under Linux"

This reverts commit cb54299.

Author: adrian-prantl

lldb/test/API/lang/swift/c_type_external_provider/TestSwiftCTypeExternalProvider.py

@@ -16,7 +16,6 @@ def setUp(self):
         self.main_source_spec = lldb.SBFileSpec(self.main_source)
 
     @swiftTest
-    @expectedFailureAll(oslist=['linux'], bugnumber='rdar://104671405')
     def test_swift_regex(self):
         """Test that C types with builtin metadata emitted are looked up using
         external type info provider."""