Update URL for "RTCMemory"

The repository name was changed again, so this is an update on the URL change made in the previous commit.

Author: per1234

registry.txt

@@ -3103,7 +3103,7 @@ https://github.com/BrandeisMakerLab/Arduino_Education.git|Contributed|Electronic
 https://github.com/Fuzzer11/SDconfig.git|Contributed|SDConfig
 https://github.com/Juerd/ESP-WiFiSettings.git|Contributed|ESP-WiFiSettings
 https://github.com/hideakitai/Debug.git|Contributed|DebugLog
-https://github.com/fabianoriccardi/RTCMemory-ESP8266.git|Contributed|RTCMemory
+https://github.com/fabianoriccardi/rtcmemory.git|Contributed|RTCMemory
 https://github.com/arbv/avr-context.git|Contributed|AVR-context
 https://github.com/hideakitai/MsgPacketizer.git|Contributed|MsgPacketizer
 https://github.com/Electro707/Simple-LED-Matrix-Library.git|Contributed|Simple LED Matrix