feat[ux]: improve hint for events kwarg upgrade

follow-on commit to ebe3c0c. the hint in ebe3c0c is
not specific to the user's source code, and it's a bit laborious for the
user to match the call-site to the event def. this commit auto-generates
the new call expression for the user to use.

vyper/semantics/types/user.py

@@ -295,10 +295,15 @@ def _ctor_call_return(self, node: vy_ast.Call) -> None:
             return validate_kwargs(node, self.arguments, self.typeclass)
 
         # warn about positional argument depreciation
-        msg = "Instantiating events with positional arguments is "
-        msg += "deprecated as of v0.4.1 and will be disallowed "
-        msg += "in a future release. Use kwargs instead eg. "
-        msg += "Foo(a=1, b=2)"
+        rec0 = ", ".join(
+            f"{argname}={val.node_source_code}"
+            for argname, val in zip(self.arguments.keys(), node.args)
+        )
+        recommendation = f"{node.func.node_source_code}({rec0})"
+        msg = "Instantiating events with positional arguments is"
+        msg += " deprecated as of v0.4.1 and will be disallowed"
+        msg += " in a future release. Use kwargs instead e.g.:"
+        msg += f"\n {recommendation}"
 
         vyper_warn(msg, node)