Bugfix FXIOS-15317 [Translations Phase 2] Settings sections display incorrect colors in Private Browsing (#32984)

Use layer5 instead of layer2 for translation settings cell backgrounds.
In the private theme, layer2 equals layer1 (both Violet90), making cells
indistinguishable from the background. layer5 (Ink20) matches the color
used by other settings cells (ThemedTableViewCell) and provides the
correct visual separation in private browsing.

Author: razvanlitianu

firefox-ios/Client/Frontend/Settings/Translation/TranslationAddLanguageCell.swift

@@ -20,6 +20,6 @@ final class TranslationAddLanguageCell: UICollectionViewListCell, ThemeApplicabl
         content.textProperties.color = theme.colors.actionPrimary
         contentConfiguration = content
         backgroundConfiguration = .listGroupedCell()
-        backgroundConfiguration?.backgroundColor = theme.colors.layer2
+        backgroundConfiguration?.backgroundColor = theme.colors.layer5
     }
 }

firefox-ios/Client/Frontend/Settings/Translation/TranslationLanguageCell.swift

@@ -24,6 +24,6 @@ final class TranslationLanguageCell: UICollectionViewListCell, ThemeApplicable {
         content.secondaryTextProperties.color = theme.colors.textSecondary
         contentConfiguration = content
         backgroundConfiguration = .listGroupedCell()
-        backgroundConfiguration?.backgroundColor = theme.colors.layer2
+        backgroundConfiguration?.backgroundColor = theme.colors.layer5
     }
 }

firefox-ios/Client/Frontend/Settings/Translation/TranslationPickerLanguageCell.swift

@@ -20,6 +20,6 @@ final class TranslationPickerLanguageCell: UITableViewCell {
         content.textProperties.color = theme.colors.textPrimary
         content.secondaryTextProperties.color = theme.colors.textSecondary
         contentConfiguration = content
-        backgroundColor = theme.colors.layer2
+        backgroundColor = theme.colors.layer5
     }
 }

firefox-ios/Client/Frontend/Settings/Translation/TranslationToggleCell.swift

@@ -25,6 +25,6 @@ final class TranslationToggleCell: UICollectionViewListCell, ThemeApplicable {
         contentConfiguration = content
         toggle.onTintColor = theme.colors.actionPrimary
         backgroundConfiguration = .listGroupedCell()
-        backgroundConfiguration?.backgroundColor = theme.colors.layer2
+        backgroundConfiguration?.backgroundColor = theme.colors.layer5
     }
 }