Fixes #16506

Problem

When a type annotation uses a call expression with keyword arguments (e.g. x: Foo(arg=1)), mypy correctly raises a [valid-type] error but also appends:

note: Suggestion: use Foo[...] instead of Foo(...)

This suggestion is misleading because Foo[arg=1] is not valid Python syntax. The suggestion only makes sense for single positional-arg calls like Foo(int), which could plausibly have been meant as Foo[int].

Fix

In mypy/fastparse.py, the suggestion in visit_Call is now only emitted when the call has exactly one positional argument and no keyword arguments.

Testing

• Added a regression test to test-data/unit/check-fastparse.test
• All 33 existing check-fastparse.test cases continue to pass
• Verified that the suggestion still correctly appears for Foo(int) style annotations

Note: I'm aware of the suggestion in the issue thread to add more context-specific notes. This PR takes the minimal approach of suppressing the incorrect suggestion; a follow-up could add more targeted messaging.