262c04f297
## Summary I noticed that augmented assignments on floats were yielding "not supported" diagnostics. If the dunder isn't bound at all, we should use binary operator semantics, rather than treating it as not-callable.
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/red_knot_test/README.md for documentation of this test format.