Fix render-to-depth-texture test;

tests/render-to-depth-texture.lua

@@ -1,4 +1,4 @@
 function lovr.load()
   t = lovr.graphics.newTexture(100, 100, { format = 'd32f' })
-  p = lovr.graphics.getPass('render', t)
+  p = lovr.graphics.getPass({ depth = t })
 end