fix i2c-dev typo

Author: MattBlack85

README.md

@@ -108,15 +108,15 @@ Adding a RTC to AstroArch is easy from version 1.6.
 First, wire your RTC to your pi, open a terminal and type `sudo i2cdetect -y 1` you should see a similar table, take note of the number for the next steps
 ![i2cdetect](https://github.com/devDucks/astroarch/assets/4163222/147f90ed-6f56-43ab-900b-0ad0c44f919c)
 
-Now find the line `dtoverlay=i2c_rtc` in `/boot/config.txt` and modify it by adding a comma and the name of your RTC device, in my case for the ds3231 will be `dtoverlay=i2c_rtc,ds3231`
+Now find the line `dtoverlay=i2c-rtc` in `/boot/config.txt` and modify it by adding a comma and the name of your RTC device, in my case for the ds3231 will be `dtoverlay=i2c-rtc,ds3231`
 
 Reboot your Raspberry PI and if you type again `sudo i2cdetect -y 1` you should now see a `UU` instead of the number, this means the kernel module for your RTC has been loaded correctly.
 
 That's all you need! We just enabled automatic modules to setup the system time from the RTC if it's present! No more steps are required!
 
 Reboot your PI and you should have the time automatically synchronized when it starts!
 
-If you want to remove the RTC sync just drop `,xxxx` from `/boot/config.txt` at line `dtoverlay=i2c_rtc,xxxx`
+If you want to remove the RTC sync just drop `,xxxx` from `/boot/config.txt` at line `dtoverlay=i2c-rtc,xxxx`
 
 # My time is not syncing from the network, what should I do?
 Some users have been reporting that the system time is not syncing whit the network, I am not sure where this problem comes from but it seems related to `timesyncd` (the utility used to sync network time) and a mobile internet network.