cmd/compile: remove inTypeCheckInl boolean

cmd/compile: remove inTypeCheckInl boolean

After CL 402974, we do not typecheck an inline body in ImportedBody
anymore, thus the inTypeCheckInl check is un-necessary.

Change-Id: Ia6154a57db507c3e00b67333f1e3b910a6de7d05
Reviewed-on: https://go-review.googlesource.com/c/go/+/402975
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>