Backport "Remove ascriptionVarargsUnpacking as we never used it" (#19475)

Backports #19399 to 3.4.0

Author: Kordyjan

compiler/src/dotty/tools/dotc/config/Feature.scala

@@ -26,7 +26,6 @@ object Feature:
   val dependent = experimental("dependent")
   val erasedDefinitions = experimental("erasedDefinitions")
   val symbolLiterals = deprecated("symbolLiterals")
-  val ascriptionVarargsUnpacking = deprecated("ascriptionVarargsUnpacking")
   val fewerBraces = experimental("fewerBraces")
   val saferExceptions = experimental("saferExceptions")
   val clauseInterleaving = experimental("clauseInterleaving")

library/src/scala/runtime/stdLibPatches/language.scala

@@ -115,9 +115,6 @@ object language:
     @compileTimeOnly("`symbolLiterals` can only be used at compile time in import statements")
     object symbolLiterals
 
-    /** TODO */
-    @compileTimeOnly("`ascriptionVarargsUnpacking` can only be used at compile time in import statements")
-    object ascriptionVarargsUnpacking
   end deprecated
 
   /** Where imported, auto-tupling is disabled.