chore: remove unused ios-specifc glutin_gles2_sys crate

This crate became unused in commit 79dab41 ("Decouple glutin from
winit") because we no longer provide iOS support, and thus far the
only crate relying on it is an old republished fork of `glutin`:
https://crates.io/crates/glutin_gles2_sys/reverse_dependencies

Author: MarijnS95

Cargo.toml

@@ -7,7 +7,6 @@ members = [
     "glutin_egl_sys",
     "glutin_glx_sys",
     "glutin_wgl_sys",
-    "glutin_gles2_sys",
 ]
 
 [workspace.package]