Change "Direct" status visibility to "Only people I mention" in web UI (#18146)

- Change name of conversations column in web UI
- Change hotkey for opening conversations column from `g d` to `g c` in web UI
- Remove shortcuts for creating direct-visibility statuses from web UI

app/javascript/mastodon/components/status_action_bar.js

@@ -266,7 +266,6 @@ class StatusActionBar extends ImmutablePureComponent {
       menu.push({ text: intl.formatMessage(messages.redraft), action: this.handleRedraftClick });
     } else {
       menu.push({ text: intl.formatMessage(messages.mention, { name: account.get('username') }), action: this.handleMentionClick });
-      menu.push({ text: intl.formatMessage(messages.direct, { name: account.get('username') }), action: this.handleDirectClick });
       menu.push(null);
 
       if (relationship && relationship.get('muting')) {