Make terminal.option_as_meta=false in default settings (#19364)

- This reverts the change I made in https://github.com/zed-industries/zed/pull/15535 which set `option_as_meta` to `true` in the default settings.
- `true` is a reasonable default for US Keyboards, but is terrible for many others which rely on `alt+<key>` for totally normal keystroke combinations.

crates/terminal/src/terminal_settings.rs

@@ -151,7 +151,7 @@ pub struct TerminalSettingsContent {
     pub alternate_scroll: Option<AlternateScroll>,
     /// Sets whether the option key behaves as the meta key.
     ///
-    /// Default: true
+    /// Default: false
     pub option_as_meta: Option<bool>,
     /// Whether or not selecting text in the terminal will automatically
     /// copy to the system clipboard.