texture_builtins.py: The unsigned integer type is "uint", not "unsigned"

This doesn't actually affect anything yet, but is good to fix anyway.

builtins/tools/texture_builtins.py

@@ -8,7 +8,7 @@ def vec_type(g, size):
         if g == "i":
             return "int"
         elif g == "u":
-            return "unsigned"
+            return "uint"
         return "float"
     return g + "vec" + str(size)