Disable commit title width limit by default (#58960)

This is a bit too opinionated to be turning on for everyone by default.
We could consider bringing back a default-enabled setting with a less
intrusive UI.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Warnings about the lengths of commit message titles are now disabled
by default.

assets/settings/default.json

@@ -998,8 +998,8 @@
     // Maximum length of the commit message title before a warning is shown.
     // Set to 0 to disable.
     //
-    // Default: 72
-    "commit_title_max_length": 72,
+    // Default: 0
+    "commit_title_max_length": 0,
   },
   "message_editor": {
     // Whether to automatically replace emoji shortcodes with emoji characters.

crates/settings_content/src/settings_content.rs

@@ -709,7 +709,7 @@ pub struct GitPanelSettingsContent {
     /// Maximum length of the commit message title before a warning is shown.
     /// Set to 0 to disable.
     ///
-    /// Default: 72
+    /// Default: 0
     pub commit_title_max_length: Option<usize>,
 }