tests: fix a missing love.graphics.pop

testing/tests/graphics.lua

@@ -2489,6 +2489,7 @@ love.test.graphics.push = function(test)
     love.graphics.setColor(1, 0, 0, 1)
     love.graphics.rectangle('fill', 0, 0, 1, 1)
     love.graphics.setColor(1, 1, 1, 1)
+    love.graphics.pop()
   love.graphics.setCanvas()
   local imgdata = love.graphics.readbackTexture(canvas)
   test:compareImg(imgdata)