ports-mgmt/portupgrade: stop warning about wrong package format

pkg expect the compression format to be set via -f option, portupgrade
passes this information extracting the PKG_SUFX variable which is now
invariable since pkg 1.17. the .pkg suffix is always used, but the -f
option still expect the compression format to be defined in same form as
before: .tar, .tbz, .tgz etc.

Remove the call to the -f format to remove a useless warning.

PR: 284054
Submitted by: Terry Kennedy <terry-freebsd@glaver.org>