Remove always-on language feature flag: AttributesToRightOfModuleKeyword

[T-Gro]

LanguageFeature.AttributesToRightOfModuleKeyword has shipped since F# 6.0 and is enabled for every selectable language version (the minimum accepted --langversion is 8.0). Its feature flag can therefore never be turned off, so it is dead configuration. This issue removes the flag and collapses the guarded code to its enabled behaviour.

What to remove

• The AttributesToRightOfModuleKeyword case in LanguageFeatures.fs and LanguageFeatures.fsi
• Its entry in the features map and its GetFeatureString arm
• The featureAttributesToRightOfModuleKeyword string in FSComp.txt
• Every SupportsFeature LanguageFeature.AttributesToRightOfModuleKeyword / checkLanguageFeatureAndRecover … AttributesToRightOfModuleKeyword guard — keep only the enabled path and delete the legacy branch
• Adjust affected tests and baselines accordingly

Consequence: --disableLanguageFeature:AttributesToRightOfModuleKeyword is no longer a recognised feature name.

Version mapping

fsharp/src/Compiler/Facilities/LanguageFeatures.fs

Line 185 in ea778bb

LanguageFeature.AttributesToRightOfModuleKeyword, languageVersion60

Feature string

fsharp/src/Compiler/FSComp.txt

Line 1254 in ea778bb

featureAttributesToRightOfModuleKeyword,"attributes to the right of the 'module' keyword"

Part of #20139