cmd/compile: clarify a few redundant deletions of internal/ssagen.state.vars
Fixes #58729
The reason why these deletions exist is that the old state.variable method
will assign the new value to the given key of map when the key doesn't exist,
but after this commit: https://github.com/golang/go/commit/
5a6e511c614a158cb58150fb62bfbc207a33922d#diff-e754f9fc8eaf878714250cfc03844eb3b58185ac806a8c1c4f9fbabd86cda921L3972
the state.variable doesn't do that anymore, thus these deletions became redundant.
Change-Id: Ie6e2471ca445f907a2bb1607c293f9301f0d73e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/471355
Run-TryBot: Andy Pan <panjf2000@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>