yaml files are always indexable

Summary:
D66928531 was wrong! The intent was to make sure yaml files are always considered indexable (even though they don't contain defined entities) but it broke the IndexablePredicate.  This caused issue as described in D67335696.

Proposed fixed is to rely on suffix.

Reviewed By: iamirzhan

Differential Revision: D67336679

fbshipit-source-id: 148e6581303bb01b94f8a23a4a76f047f7f5dd3e

glean/schema/source/codemarkup.angle

@@ -905,6 +905,8 @@ predicate IndexedFile: src.File
    File where
     codemarkup.cxx.CxxDataAvailable File |
     codemarkup.EntityDataAvailable File |
+    # All Yaml files are indexable, even though they don't
+    # contain entities
     codemarkup.yaml.YamlDataAvailable File
 
 # Identifies files with indexed entities.

glean/schema/source/codemarkup.yaml.angle

@@ -24,6 +24,6 @@ schema codemarkup.yaml.1 {
     yaml.XRefViaName { source = S , decl = { just = D } } = XRefs[..];
 
     predicate YamlDataAvailable : src.File
-    F where
-        src.File _ = F
+      F where yaml.XRefsByFile {file = F}
+
 }