Add missing field to impl Hash for RenderGlyphParams (#20316)

Unlikely to cause any behavior change but seems more correct to include
`is_emoji` in the hash.

Release Notes:

- N/A

crates/gpui/src/text_system.rs

@@ -668,6 +668,7 @@ impl Hash for RenderGlyphParams {
         self.font_size.0.to_bits().hash(state);
         self.subpixel_variant.hash(state);
         self.scale_factor.to_bits().hash(state);
+        self.is_emoji.hash(state);
     }
 }