Do not highlight non translated things in Interlingua

The technical terms are usually same as in English, so this yields
warnings too often.
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/checks/same.py

@@ -1135,7 +1135,8 @@ class SameCheck(TargetCheck):
 
     def check_single(self, source, target, unit, cache_slot):
         # English variants will have most things not translated
-        if self.is_language(unit, ('en', )):
+        # Interlingua is also quite often similar to English
+        if self.is_language(unit, ('en', 'ia')):
             return False
 
         # One letter things are usually labels or decimal/thousand separators