Move shairport-sync manual from section 7 to 1

Move shairport-sync manual from section 7 to 1

From mandoc man(1) [-s] section:
                   1         General commands (tools and utilities).
                   [...]
                   7         Miscellaneous information.

From GNU man(1) DESCRIPTION:
     1   Executable programs or shell commands
     [...]
     7   Miscellaneous (including macro packages and conventions), e.g.
         man(7), groff(7)

shairport-sync is an executable, shairport-sync(1) ought to be its
documentation, not merely miscellaneous information.

OpenBSD adjusts this in its audio/shairport-sync port/package ever since.