mute failing test in 20_mix_typeless_typeful

awaits fix in elastic#39198

Author: talevy

rest-api-spec/src/main/resources/rest-api-spec/test/indices.create/20_mix_typeless_typeful.yml

@@ -104,8 +104,8 @@
 "Implicitly create a typeless index while there is a typed template":
 
  - skip:
-      version: " - 6.99.99"
-      reason: needs typeless index operations to work on typed indices
+      version: "all"
+      reason: "awaits fix in #39198"
 
  - do:
       indices.put_template: