MFH: r552342

Revert meld update to 3.21.0. This version requires pygobject 3.30
which is not present in the ports tree and fails to start at runtime.

Bump PORTEPOCH.

Reviewed by: bapt
Approved by: bapt, portmgr (fixit)
Differential Revision: https://reviews.freebsd.org/D26775

Approved by: portmgr (implicit, runtime fix)