ws: Stop setting G_TLS_GNUTLS_PRIORITY
ws: Stop setting G_TLS_GNUTLS_PRIORITY

This was done 5 years ago in commit 0750a1024586d23 to disable SSL3.
This is the default these days, and that setting is now invalid with
recent GnuTLS/glib versions:

    G_TLS_GNUTLS_PRIORITY is invalid; ignoring

Drop it and rely on the OS defaults. Our integration test will still
make sure that SSL3 and other old ciphers won't work.

Closes #14179
mvollmer/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,garrett/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit