git_ui: Fix indent guides not showing for file buffers in the commit view (#44166)

Follow up to https://github.com/zed-industries/zed/pull/44162 where my
strategy for not displaying the indent guides only in the commit message
was wrong given I ended up... disabling indent guides for all the
buffers. This PR adds a new method to the editor where we can disable it
for a specific buffer ID following the pattern of
`disable_header_for_buffer`.

Release Notes:

- N/A

crates/git_ui/src/commit_view.rs

@@ -150,7 +150,6 @@ impl CommitView {
                 Editor::for_multibuffer(multibuffer.clone(), Some(project.clone()), window, cx);
 
             editor.disable_inline_diagnostics();
-            editor.disable_indent_guides();
             editor.set_expand_all_diff_hunks(cx);
 
             editor
@@ -259,6 +258,8 @@ impl CommitView {
 
                 this.editor.update(cx, |editor, cx| {
                     editor.disable_header_for_buffer(message_buffer.read(cx).remote_id(), cx);
+                    editor
+                        .disable_indent_guides_for_buffer(message_buffer.read(cx).remote_id(), cx);
 
                     editor.insert_blocks(
                         [BlockProperties {