Correct descriptions of M1 & M2 per RFC 5054

[cipherboy]

As far as I can tell from the code, what is defined as:

key = compute_premaster_secret(...)

does not include the given hash invocation step. While RFC 5054 is unclearly worded (see comment below), SRP-6 is clear that M1 should not include K = H(S) and thus this description of the protocol is incorrect. As far as I can tell, nobody else uses this computation of M1 (with K = H(S) as a parameter) and thus it should be dropped from the tabular and comment descriptions.

See also: https://github.com/bcgit/bc-csharp/issues/506#issuecomment-1932665252

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Edit to add: regardless of which spec is deemed correct or supported or implemented (SPR-6 or RFC 2945) -- it is clear that M1 = H(A, B, H(S)) is not aligning with either of those two, and also (I believe) wasn't implemented in the code.