guide: Drop obsolete "SSL Versions and Ciphers" section
guide: Drop obsolete "SSL Versions and Ciphers" section

Customizing `G_TLS_GNUTLS_PRIORITY` was dropped in commit 8d832e78f, so
this does not apply any more.

Closes #14228
moraleslazaro/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,deryni/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,garrett/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,martinpitt/cockpit,garrett/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,cockpit-project/cockpit,garrett/cockpit,mvollmer/cockpit,deryni/cockpit,cockpit-project/cockpit,garrett/cockpit,moraleslazaro/cockpit