cmd/cgo: fix unexpected semicolon in rewritten line

Followup to CL 157961 and CL 158457.
Finish the list of operators and punctuation
that disable semicolon insertion at end-of-line
The reported case was "(" but "." was also missing.

Fixes #31017.

Change-Id: I0c06443f38dc8250c62e3aadd104abfa0e3be074
Reviewed-on: https://go-review.googlesource.com/c/go/+/174524


Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>