fix: revert skip validation

[shaffeeullah]

Fixes https://github.com/googleapis/nodejs-storage/issues/709

[shaffeeullah]

@frankyn i think this system test is failing because it's not returning the 'x-goog-stored-content-encoding' header. is that supposed to happen automatically?

[shaffeeullah]

I think we need some integration tests to associate with the new behavior

There are already integration tests associated with this new boolean.

False case: https://github.com/googleapis/nodejs-storage/blob/0845525a9aebd94da92882ace4cd29bf125641a2/system-test/storage.ts#L2181

True case: https://github.com/googleapis/nodejs-storage/blob/0845525a9aebd94da92882ace4cd29bf125641a2/system-test/storage.ts#L2148

There are also a few unit tests verifying that validation happens correctly. (Let me know if you'd like me to link those. I know they exist because I originally broke them with this change; they're doing good work!)

[shaffeeullah]

One last nit, @shaffeeullah, this will be blocked until the header is no longer allowlist required.

@frankyn What is the timeline for that?

[shaffeeullah]

@frankyn says this is launched, clear to merge