chore(docs): bigtable typehint for exactMatch

[bshaffer]

BigTable typehints for exactMatch functions are passed to RegexTrait::escapeLiteralValue, which accepts array|string. This is seen in our samples as well (the result of unpack is an array).

This was caught by static analysis. I believe these methods should be widened to also accept arrays.

[bshaffer]

Looking at RegexTrait::escapeLiteralValue, if the samples pass in scalar '1' instead of unpack('C*', 1), the result is the same. Is this the preferred method? If so, we should just fix the samples.

[vishwarajanand]

I think this approach is better than editing the samples AND the escapeLiteralValue docblock.

[dwsupplee]

Thank you!