Update MSRV to 1.80 (#5457)

Because some dependencies now require it, see:
* https://github.com/emilk/egui/pull/5456

crates/epaint/src/texture_handle.rs

@@ -66,6 +66,7 @@ impl TextureHandle {
     }
 
     /// Assign a new image to an existing texture.
+    #[allow(clippy::needless_pass_by_ref_mut)] // Intentionally hide interiority of mutability
     pub fn set(&mut self, image: impl Into<ImageData>, options: TextureOptions) {
         self.tex_mngr
             .write()
@@ -73,6 +74,7 @@ impl TextureHandle {
     }
 
     /// Assign a new image to a subregion of the whole texture.
+    #[allow(clippy::needless_pass_by_ref_mut)] // Intentionally hide interiority of mutability
     pub fn set_partial(
         &mut self,
         pos: [usize; 2],