extmod/modwebrepl: Use bigger socket receive buffer.

The smaller chunks we send (and receive), the more packets there to
receive, and higher chance to git internal packet buffer overflow in
WiFi driver.

extmod/modwebrepl.c

@@ -195,7 +195,7 @@ STATIC mp_uint_t _webrepl_read(mp_obj_t self_in, void *buf, mp_uint_t size, int
     }
 
     if (self->data_to_recv != 0) {
-        static byte filebuf[256];
+        static byte filebuf[512];
         filebuf[0] = *(byte*)buf;
         mp_uint_t buf_sz = 1;
         if (--self->data_to_recv != 0) {