Remove -Yforce-inline-while-typing (scala#19889)

This flag only existed to help the migration to 3.0.0 from preview
builds older than `3.0.0-M3`. This was only relevant for the 3.0.X
versions.

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

@@ -435,8 +435,6 @@ private sealed trait YSettings:
   val Yinstrument: Setting[Boolean] = BooleanSetting("-Yinstrument", "Add instrumentation code that counts allocations and closure creations.")
   val YinstrumentDefs: Setting[Boolean] = BooleanSetting("-Yinstrument-defs", "Add instrumentation code that counts method calls; needs -Yinstrument to be set, too.")
 
-  val YforceInlineWhileTyping: Setting[Boolean] = BooleanSetting("-Yforce-inline-while-typing", "Make non-transparent inline methods inline when typing. Emulates the old inlining behavior of 3.0.0-M3.")
-
   val YdebugMacros: Setting[Boolean] = BooleanSetting("-Ydebug-macros", "Show debug info when quote pattern match fails")
 
   // Pipeline compilation options

compiler/src/dotty/tools/dotc/inlines/Inlines.scala

@@ -81,7 +81,6 @@ object Inlines:
   private def needsTransparentInlining(tree: Tree)(using Context): Boolean =
     tree.symbol.is(Transparent)
     || ctx.mode.is(Mode.ForceInline)
-    || ctx.settings.YforceInlineWhileTyping.value
 
   /** Try to inline a call to an inline method. Fail with error if the maximal
    *  inline depth is exceeded.