Multi-Language Support: Revert the GUI Warning

[gregory-paidis-sonarsource]

We have a GUI Warning that notifies the user of the new feature, and suggests that they can turn if off with /d:sonar.scanner.scanAll=false.

We should revert this in X months, when the feature is well established.

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When removing this warning, revert this PR in sonar-dotnet: SonarSource/sonar-dotnet#9635

[KeesCBakker]

Any luck on this? Maybe we can remove the warning when /d:sonar.scanner.scanAll=true is specified?

[michha]

If removing the warning is done for 2025.2 or 2025.3 this should be backported to 2025.1.1 so its also in the LTA version