For #15910 - Adds back automatic toggle, disables slider when enabled

[ekager]

We want to undo this and just disable the slider while auto is enabled

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

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[codecov-io]

Codecov Report

Merging #16070 into master will increase coverage by 0.00%.
The diff coverage is 27.27%.

@@            Coverage Diff            @@
##             master   #16070   +/-   ##
=========================================
  Coverage     29.75%   29.76%           
  Complexity     1191     1191           
=========================================
  Files           453      453           
  Lines         18481    18489    +8     
  Branches       2539     2542    +3     
=========================================
+ Hits           5499     5503    +4     
- Misses        12562    12567    +5     
+ Partials        420      419    -1     

Impacted Files	Coverage Δ	Complexity Δ
...src/main/java/org/mozilla/fenix/components/Core.kt	21.65% <0.00%> (ø)	1.00 <0.00> (ø)
...rg/mozilla/fenix/settings/AccessibilityFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../fenix/settings/TextPercentageSeekBarPreference.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
.../src/main/java/org/mozilla/fenix/utils/Settings.kt	69.89% <100.00%> (+0.32%)	35.00 <0.00> (ø)
app/src/main/java/org/mozilla/fenix/Config.kt	54.54% <0.00%> (+4.54%)	2.00% <0.00%> (ø%)

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[gabrielluong]

r+ assuming we fix the line.