Edit Mesh: Fix interpolation of gradient on edit edges

This fix some issue with the AA on edit mesh edges.

source/blender/draw/modes/shaders/edit_mesh_overlay_frag.glsl

@@ -16,7 +16,7 @@ uniform float edgeScale;
 
 flat in vec4 finalColorOuter_f;
 in vec4 finalColor_f;
-in float edgeCoord_f;
+noperspective in float edgeCoord_f;
 
 out vec4 FragColor;
 

source/blender/draw/modes/shaders/edit_mesh_overlay_geom.glsl

@@ -12,7 +12,7 @@ in int selectOveride[2];
 
 flat out vec4 finalColorOuter_f;
 out vec4 finalColor_f;
-out float edgeCoord_f;
+noperspective out float edgeCoord_f;
 
 void do_vertex(const int i, vec4 pos, float coord, vec2 offset)
 {