Revert terminal: Add Alt key bindings for terminal (#15535)

- reverts commit 66ada3e44c.
- change default `option_as_meta` to true

crates/terminal/src/terminal_settings.rs

@@ -141,7 +141,7 @@ pub struct TerminalSettingsContent {
     pub alternate_scroll: Option<AlternateScroll>,
     /// Sets whether the option key behaves as the meta key.
     ///
-    /// Default: false
+    /// Default: true
     pub option_as_meta: Option<bool>,
     /// Whether or not selecting text in the terminal will automatically
     /// copy to the system clipboard.