[LINTER] Prevent updating { (void)foo() } to { ()foo }

Summary:
The CppVoidParameterLinter can be unexpectedly confused by the use of
(void) to discard a function return value if it's not on it's own
line. This diff improves the regex to fix this edge case.

Test Plan:
Add { (void)foo() } to some source file and check the linter don't
trigger anymore. Check it still triggers as expected on foo(void) {}.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D9214