Resolve unnecessary_map_or clippy lint

    warning: this `map_or` is redundant
      --> diagram/src/main.rs:16:25
       |
    16 |             *pixel = if char::from_u32(row * width + col).map_or(false, f) {
       |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use is_some_and instead: `char::from_u32(row * width + col).is_some_and(f)`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_map_or
       = note: `-W clippy::unnecessary-map-or` implied by `-W clippy::all`
       = help: to override `-W clippy::all` add `#[allow(clippy::unnecessary_map_or)]`

Author: dtolnay

diagram/src/main.rs

@@ -13,7 +13,7 @@ fn main() {
     for (name, f) in diagrams {
         let mut imgbuf = ImageBuffer::new(width, height);
         for (col, row, pixel) in imgbuf.enumerate_pixels_mut() {
-            *pixel = if char::from_u32(row * width + col).map_or(false, f) {
+            *pixel = if char::from_u32(row * width + col).is_some_and(f) {
                 Rgb([0u8, 0, 0])
             } else {
                 Rgb([255, 255, 255])