Revert "fix scala#14626"

Scratch that, it was causing the desugaring to include a withFilter
which I believe is undesirable here.

This reverts commit 9c26189.

Author: griggt

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1582,7 +1582,7 @@ object desugar {
         if gen.checkMode == GenCheckMode.FilterAlways then // pattern was prefixed by `case`
           false
         else
-          gen.checkMode == GenCheckMode.Ignore
+          gen.checkMode != GenCheckMode.FilterNow
           || isVarBinding(gen.pat)
           || isIrrefutable(gen.pat, gen.expr)