Add test case that we now parse empty generic disambiguation lists

Author: ahoppen

Tests/SwiftParserTest/translated/GenericDisambiguationTests.swift

@@ -237,8 +237,7 @@ final class GenericDisambiguationTests: XCTestCase {
   func testGenericDisambiguation15() {
     AssertParse(
       """
-      // TODO: parse empty <> list
-      //A<>.c() // e/xpected-error{{xxx}}
+      A<>.c()
       """
     )
   }