Re-enable MSVC C4204 diagnostic; NFC (#182491)
From MSDN:
https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-4-c4204?view=msvc-170
> nonstandard extension used : non-constant aggregate initializer
This is an ANSI compatibility diagnostic which isn't useful for us to
disable. In my local testing, this diagnostic is not emitted.
