Remove remaining SalesforceReact references

[wmathurin]

Summary

• Removed android-nightly-React job from nightly workflow
• Removed React Native Dependencies step from reusable lib workflow
• Removed SalesforceReact from Danger's LIBS array, codecov config, and READMEs
• Added a note in root README indicating SalesforceReact moved to SalesforceMobileSDK-ReactNative in SDK 14.0

Test plan

• Verify nightly workflow triggers correctly without the React job
• Verify PR workflows still detect modified libs correctly
• Confirm codecov reporting works for remaining libraries

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.41%. Comparing base (fdb090a) to head (0ec99fc).
⚠️ Report is 18 commits behind head on dev.

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #2906      +/-   ##
============================================
+ Coverage     66.40%   66.41%   +0.01%     
- Complexity     3097     3099       +2     
============================================
  Files           226      226              
  Lines         17774    17774              
  Branches       2327     2327              
============================================
+ Hits          11802    11804       +2     
  Misses         4896     4896              
+ Partials       1076     1074       -2     

Components	Coverage Δ
Analytics	48.71% <ø> (ø)
SalesforceSDK	62.53% <ø> (+0.02%)	⬆️
Hybrid	59.30% <ø> (ø)
SmartStore	78.22% <ø> (ø)
MobileSync	82.12% <ø> (ø)
see 2 files with indirect coverage changes

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