man/man2/msync.2: HISTORY: Update POSIX appearances of msync(2)

man/man2/msync.2: HISTORY: Update POSIX appearances of msync(2)

msync(2) appeared in SUSv1.[1]  The function was then added to
POSIX.1-1996.[2]

[1] X/Open CAE Specification, System Interfaces and Headers Issue 4,
Version 2, Chapter 3 "System Interfaces", pp. 412-413.
[2] ISO/IEC 9945-1:1996, Section 12.2.4 "Memory Object Synchronization".

Signed-off-by: Seth McDonald <sethmcmail@pm.me>
Message-ID: <d106bca86ec14c722b31febfaae0bdea6afbd8b2.1769429341.git.sethmcmail@pm.me>
Signed-off-by: Alejandro Colomar <alx@kernel.org>