[JS] Remove the last remaining legacy backend code

[Sergej Jaskiewicz (broadwaylamb)]

RIP

[kotlin-safemerge]

Code Owners

Rule	Owners	Approval
**.​gradle.​kts, /​repo/​	@sellmair kotlin-build-infrastructure @goodwinnk @Badya @4u7 @tbogdanova @CristianGM @SmialyKot @ozzush @kbrgnj	❌ UNASSIGNED
/​analysis/​, /​compiler/​psi/​	kotlin-analysis-api @yanex @marcopennekamp @abelkov @dimonchik0036 @BlaBlaHuman	❌ UNASSIGNED
/​build-​common/​	build-tools-api @wojtek-kalicinski @ALikhachev @Herudaio @ywett02 @shinkai-tester kotlin-build-tools @AYastrebov @Tapchicoma @antohaby @Herudaio @atyrin @CherepanovAleksei @rbbozkurt @shinkai-tester @viakunin @levchenkoin @adam-enko	❌ UNASSIGNED
/​compiler/​daemon/​	build-tools-api @wojtek-kalicinski @ALikhachev @Herudaio @ywett02 @shinkai-tester	❌ UNASSIGNED
/​compiler/​test-​infrastructure-​utils/​	kotlin-frontend @ligee @dzharkov @bnorm @mglukhikh @KvanTTT @cypressious @demiurg906 @FenstonSingel @agamzikova @GrigoriiSolnyshkin @Aleksandra-Arsenteva	❌ UNASSIGNED
*	kotlin @klikh @antonarhipov @singleton11 @AYastrebov @wojtek-kalicinski @ALikhachev @shengyou @svtk @Tapchicoma @joffrey-bion @shishkin-pavel @SebastianAigner @qwwdfsad @antohaby @eupp @ilya-g @shanshin @abarsov @pahill @Herudaio @atyrin @DmitryNekrasov @vmishenev @sandwwraith @zsmb13 @nomisRev @utikeev @fzhinkin @AbdullinAM @ywett02 @strangepleasures @Jeffset @CherepanovAleksei @solarday @Frame17 @sellmair @barinsim @rbbozkurt @whyoleg @shinkai-tester @viakunin @Daria-Voronina @levchenkoin @molczane @adam-enko @ai-volkov @semyonsushich kotlin-compiler @erokhins kotlin-frontend @ligee @dzharkov @bnorm @mglukhikh @KvanTTT @cypressious @demiurg906 @FenstonSingel @agamzikova @GrigoriiSolnyshkin @Aleksandra-Arsenteva kotlin-wasm @bashor @karlosz @ilgonmic @jmrtsh @igoriakovlev @agamzikova @alex28sh @ozzush kotlin-jvm @udalov @ilmirus @grechkovlad @zhelenskiy @aShalygin @andrey-mogilev kotlin-js @JSMonk @broadwaylamb @seclerp @AnzhelaSukhanova kotlin-common-backend @vsukharev @kunyavskiy @ivandev0 @AnzhelaSukhanova @mcpiroman @ddolovov @mpiekutowski kotlin-native @mMaxy @projedi @anton-bannykh @sbogolepov @DmT021 @haitaka @glukianets @azakharenko @homuroll @SvyatoslavScherbina kotlin-language-evolution @serras @jesyspa @ice-phoenix @zarechenskiy @watc4d0gg @FenstonSingel @InversionSpaces @e2e4b6b7 @YuliaKorolenko	❌ UNASSIGNED
/​js/​	kotlin-js @JSMonk @broadwaylamb @seclerp @AnzhelaSukhanova	❌ UNASSIGNED

[kodee-bot]

This merge request potentially modifies the stubs format, but doesn't update KotlinStubVersions.kt.
Please verify whether a stub version bump is needed in compiler/psi/psi-api/src/org/jetbrains/kotlin/psi/stubs/KotlinStubVersions.kt.
If you are unsure, please consult with the Analysis API team (#kotlin-analysis-api in Slack).