gl renderer: Remove unused shaders

gsk/meson.build

@@ -8,9 +8,6 @@ gsk_private_source_shaders = [
   'resources/glsl/color_matrix.fs.glsl',
   'resources/glsl/color_matrix.vs.glsl',
   'resources/glsl/linear_gradient.fs.glsl',
-  'resources/glsl/linear_gradient.vs.glsl',
-  'resources/glsl/rounded_clip.fs.glsl',
-  'resources/glsl/clip.fs.glsl',
   'resources/glsl/es2_common.fs.glsl',
   'resources/glsl/es2_common.vs.glsl',
   'resources/glsl/gl3_common.fs.glsl',

gsk/resources/glsl/linear_gradient.vs.glsl

@@ -1,5 +0,0 @@
-void main() {
-  gl_Position = uMVP * vec4(aPosition, 0.0, 1.0);
-
-  vUv = vec2(aUv.x, aUv.y);
-}