bugfix: Revert the change in scala#23438 and leave only the test

Author: tgodzik

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -125,7 +125,7 @@ object TypeOps:
   def isLegalPrefix(pre: Type)(using Context): Boolean =
     // isLegalPrefix is relaxed after typer unless we're doing an implicit
     // search (this matters when doing summonInline in an inline def like in tests/pos/i17222.8.scala).
-    pre.isStable || !ctx.phase.isTyper && ctx.mode.is(Mode.ImplicitsEnabled)
+    pre.isStable || !ctx.phase.isTyper
 
   /** Implementation of Types#simplified */
   def simplify(tp: Type, theMap: SimplifyMap | Null)(using Context): Type = {