render/gles2: de-duplicate vertex shaders

The vertex shaders for quads and textures are identical.

render/gles2/shaders/meson.build

@@ -1,9 +1,8 @@
 embed = find_program('./embed.sh', native: true)
 
 shaders = [
-	'quad.vert',
+	'common.vert',
 	'quad.frag',
-	'tex.vert',
 	'tex_rgba.frag',
 	'tex_rgbx.frag',
 	'tex_external.frag',

render/gles2/shaders/tex.vert

@@ -1,9 +0,0 @@
-uniform mat3 proj;
-attribute vec2 pos;
-attribute vec2 texcoord;
-varying vec2 v_texcoord;
-
-void main() {
-	gl_Position = vec4(proj * vec3(pos, 1.0), 1.0);
-	v_texcoord = texcoord;
-}