package/msmtp: drop unneeded static openssl workaround

package/msmtp: drop unneeded static openssl workaround

msmtp uses pkg-config to find openssl dependencies such as lz or latomic
so drop unneeded openssl workaround that was added by
https://git.buildroot.net/buildroot/commit/package/msmtp?id=468bbc1538aaea87beaf455a2ad6ea5a255d5f58

I don't know why it was added seven years ago as msmtp already used
pkg-config at this time:
https://github.com/marlam/msmtp-mirror/blob/rel-1-4-27/configure.ac

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>