Remove the assertion against functions bound to types for which should not be possible

- The list was wrong - we do support string and int literals
- The assertion was meant to guard against silently skipping over types for which there is no special handling. The current code handles everything in a generic way though and likely will not have to be adjusted for newly added types so the risk of that happening is low.

test/libsolidity/semanticTests/libraries/internal_library_function_bound_to_literal.sol

@@ -0,0 +1,26 @@
+library L {
+    function double(uint a) internal pure returns (uint) {
+        return a * 2;
+    }
+
+    function double(bytes memory a) internal pure returns (bytes memory) {
+        return bytes.concat(a, a);
+    }
+}
+
+contract C {
+    using L for *;
+
+    function double42() public returns (uint) {
+        return 42.double();
+    }
+
+    function doubleABC() public returns (bytes memory) {
+        return "abc".double();
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// double42() -> 84
+// doubleABC() -> 0x20, 6, "abcabc"