Removed std::fmt::Display requirement for TextBuffer.

Now uses the `AsRef<str>` impl to format it where applicable.

egui/src/widgets/text_edit.rs

@@ -113,7 +113,7 @@ impl CCursorPair {
 /// an underlying buffer.
 ///
 /// Most likely you will use a `String` which implements `TextBuffer`.
-pub trait TextBuffer: AsRef<str> + Into<String> + std::fmt::Display {
+pub trait TextBuffer: AsRef<str> + Into<String> {
     /// Inserts text `text` into this buffer at character index `ch_idx`.
     ///
     /// # Notes