users: Turn č and ç to c when suggesting a username
users: Turn č and ç to c when suggesting a username

These letters were already in the translation table, but the character
set parens were missing from the regular expression.

Closes #11412
moraleslazaro/cockpit,martinpitt/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,garrett/cockpit,deryni/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,garrett/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,cockpituous/cockpit,garrett/cockpit,martinpitt/cockpit,cockpituous/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,garrett/cockpit,deryni/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpituous/cockpit,deryni/cockpit,cockpit-project/cockpit,cockpituous/cockpit,deryni/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpituous/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit