[flow][cleanup][EZ] Kill RequiredInlineKeyof variant of mapped type…

… error

Summary:
Unused because it's supported

Changelog: [internal]

Reviewed By: gkz

Differential Revision: D56271320

fbshipit-source-id: d744e7356f6c28713d7785d62b23406d6ab97fe3

src/typing/debug_js.ml

@@ -1962,7 +1962,6 @@ let dump_error_message =
           match kind with
           | InterfaceOrDeclaredClass -> "InterfaceOrDeclaredClass"
           | ExtraProperties -> "ExtraProperties"
-          | RequiredInlineKeyof -> "RequiredInlineKeyof"
           | ExplicitExactOrInexact -> "ExplicitExactOrInexact"
           | RemoveOptionality -> "RemoveOptionality"
         )

src/typing/errors/error_message.ml

@@ -872,7 +872,6 @@ and ts_syntax_kind =
 and invalid_mapped_type_error_kind =
   | InterfaceOrDeclaredClass
   | ExtraProperties
-  | RequiredInlineKeyof
   | ExplicitExactOrInexact
   | RemoveOptionality
 
@@ -5300,13 +5299,6 @@ let friendly_message_of_msg loc_of_aloc msg =
         [text "Mapped Types are not supported in interfaces or declared classes."]
       | ExtraProperties ->
         [text "Mapped Types cannot be used when other properties or indexers are present."]
-      | RequiredInlineKeyof ->
-        [
-          text
-            "Fully general mapped types are not supported yet. All mapped types must use an inline keyof: ";
-          code "{[key in keyof O]: T}";
-          text ".";
-        ]
       | ExplicitExactOrInexact ->
         [
           text "Mapped Types take on the exactness of the argument passed to keyof. They do not ";