fix: Emit type apply synthetics

Most of the type apply synthetics have disappeared in
scala#15877
because, previously we relies on the `Scala2` flag
for filtering out TypeApply synthetics.

However, it was hacky, and the capture checking PR
makes change on how the compiler put the flags to symbols.
As a result, most TypeApply synthetics have disappeared.

this commit revives those disappeared type apply synthetics.

Author: tanishiking

compiler/src/dotty/tools/dotc/semanticdb/SyntheticsExtractor.scala

@@ -26,7 +26,7 @@ class SyntheticsExtractor:
       tree match
         case tree: TypeApply
           if tree.span.isSynthetic &&
-            tree.args.forall(arg => !arg.symbol.is(Scala2x)) &&
+            tree.args.forall(arg => !arg.symbol.isDefinedInSource) &&
             !tree.span.isZeroExtent =>
           visited.add(tree)
           val fnTree = tree.fun match