qt5-network: Drop some patches for old LibreSSL versions.

[rakuco]

Summary

The ports tree currently has LibreSSL 2.7.3, so remove some patches added to
support LibreSSL < 2.5. Cleaning up our existing patches also helps us move
to Qt 5.10.

Test Plan

Everything still applies, but I have not checked if LibreSSL still works, so help there is appreciated.

[brnrd]

qt-network is broken with current versions of LibreSSL in the tree. Need to check if there's a patch somewhere now...
Perhaps hang on until a patch surfaces?

[rakuco]

Do you have an ETA? If you still need to look for the new patches and get them to apply, I'd rather move along with this one to help us move quicker to Qt 5.10 -- as I see it, the tree is already broken with LibreSSL and you'd need to refresh the patches for 5.10 anyway.

[tcberner]

If it makes the import of 5.10 faster, I'm fine with this.