ports: Enable ure.sub() on stm32, esp8266 (not 512k) and esp32.
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index aeb8c44..495861b 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -122,6 +122,7 @@
 #define MICROPY_PY_UZLIB                    (1)
 #define MICROPY_PY_UJSON                    (1)
 #define MICROPY_PY_URE                      (1)
+#define MICROPY_PY_URE_SUB                  (1)
 #define MICROPY_PY_UHEAPQ                   (1)
 #define MICROPY_PY_UTIMEQ                   (1)
 #define MICROPY_PY_UHASHLIB                 (1)