Ensure muiltibuffer anchors are contained within their excerpt ranges

Co-Authored-By: Nathan Sobo <nathan@zed.dev>
Co-Authored-By: Antonio Scandurra <me@as-cii.com>

crates/editor/src/multi_buffer/anchor.rs

@@ -14,13 +14,6 @@ pub struct Anchor {
 }
 
 impl Anchor {
-    pub fn new(excerpt_id: ExcerptId, text_anchor: text::Anchor) -> Self {
-        Self {
-            excerpt_id,
-            text_anchor,
-        }
-    }
-
     pub fn min() -> Self {
         Self {
             excerpt_id: ExcerptId::min(),