Log Message:
pkgin: Update to 20.7.0.

Update pkg_install dependency for "pkg_admin rebuild-tree" fixes.

## Version 20.7.0 (2020-07-13)

 * Order package installs correctly.
 * Switch to mdoc(7) manual page, converted by wizd(8).
 * Remove -F (force reinstall) flag.
 * Enable compiler warnings in maintainer mode.
 * Match candidate packages correctly, avoiding issues with packages that
   include "-[0-9]" in their package names.
 * Various internal cleanups.