lossless is slow

just make it as fast as can be - same as 6fc0e28

xpra/codecs/pillow/encoder.py

@@ -178,7 +178,7 @@ def encode(coding : str, image, options):
             kwargs["optimize"] = True
         elif coding=="webp" and q>=100:
             kwargs["lossless"] = 1
-            kwargs["quality"] = max(0, 50-speed//2)
+            kwargs["quality"] = 0
         pil_fmt = coding.upper()
     else:
         assert coding in ("png", "png/P", "png/L"), "unsupported encoding: %s" % coding