enable neighbours feature for all repeater variants

variants/heltec_v2/platformio.ini

@@ -28,6 +28,7 @@ build_flags =
   -D ADVERT_LAT=0.0
   -D ADVERT_LON=0.0
   -D ADMIN_PASSWORD='"password"'
+  -D MAX_NEIGHBOURS=8
 ;  -D MESH_PACKET_LOGGING=1
 ;  -D MESH_DEBUG=1
 build_src_filter = ${Heltec_lora32_v2.build_src_filter}