Fix road labels letter orientation (#1751)

Fixes the bad orientation of a letter reported in https://github.com/openmaptiles/openmaptiles/issues/1750. Fixes any other potential weird letter rendering from zoom level 17 to 20 by making the symbol-spacing bigger at these zooms.

layers/transportation_name/style.json

@@ -74,8 +74,10 @@
             "zoom"
           ],
           250,
+          17,
+          400,
           20,
-          600,
+          800,
           21,
           1100
         ],