Remove pprTrace from pushCoercionIntoLambda (#21555)

This firstly caused spurious output to be emitted (as evidenced by #21555 (closed)) but even worse caused a massive coercion to be attempted to be printed (> 200k terms) which would invariably each up all the memory of your computer.

The good news is that removing this trace allows the program to compile to completion, the bad news is that the program exhibits a core lint error (on 9.0.2) but not any other releases it seems.

Fixes #21577 (closed) and #21555 (closed)