Update ref to react-native-slider fork to support autolinking

[lukewalczak]

Fixes app crash on opening settings within Spacer, because of missing RNCSlider after updating RN.

During the building process you could notice a warning:

[!] use_native_modules! skipped the react-native dependency '@react-native-community/slider'. No podspec file was found.

I assume that autolinking requires podspec file to be on the project root, but in react-native-slider is nested so I had to move up.

To test:

1. remove old node_modules
2. yarn clean:install
3. yarn ios
4. add a Spacer block
5. open settings
6. app mustn't crash!

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[chipsnyder]

LGTM Thanks for taking care of this!

As a helpful note to others, I was getting a CocoaPods error, and I had to clear my Derived Data as well.