render: completely disable gles2 if requested but libEGL is found

For `required` to disable search the value needs to be of `feature` type.
Checking `gles2` via `in` keyword returns a `bool` but `required: false`
makes the dependency optional instead of disabled.

render/meson.build

@@ -14,13 +14,12 @@ wlr_files += files(
 	'wlr_texture.c',
 )
 
-egl = dependency('egl', required: 'gles2' in renderers)
-if egl.found()
-	wlr_deps += egl
-	wlr_files += files('egl.c')
-endif
-
 if 'gles2' in renderers or 'auto' in renderers
+	egl = dependency('egl', required: 'gles2' in renderers)
+	if egl.found()
+		wlr_deps += egl
+		wlr_files += files('egl.c')
+	endif
 	subdir('gles2')
 endif