render: OpenGL and GLES2 should explicitly request a not-sRGB-capable context.

Reference Issue #14898.

src/render/opengl/SDL_render_gl.c

@@ -1838,6 +1838,7 @@ static bool GL_CreateRenderer(SDL_Renderer *renderer, SDL_Window *window, SDL_Pr
 
     renderer->name = GL_RenderDriver.name;
 
+    SDL_GL_SetAttribute(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, 0);
     data->context = SDL_GL_CreateContext(window);
     if (!data->context) {
         goto error;

src/render/opengles2/SDL_render_gles2.c

@@ -2394,6 +2394,7 @@ static bool GLES2_CreateRenderer(SDL_Renderer *renderer, SDL_Window *window, SDL
     renderer->name = GLES2_RenderDriver.name;
 
     // Create an OpenGL ES 2.0 context
+    SDL_GL_SetAttribute(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, 0);
     data->context = SDL_GL_CreateContext(window);
     if (!data->context) {
         goto error;