Dedent your yields!
Fixes a surprising interaction between the generator system in linear_util.py
and the try/finally python context managers we use for managing tracing context.
The `finally` block wasn't always being called until garbage collection, so the
context stack pushes/pops weren't always correctly nested. Dedenting the yield
fixes this particular bug but long-term we should get rid of linear_util
altogether.
PiperOrigin-RevId: 695898528
