flow [nfc]: Use $FlowIgnore where we used to use `$FlowMigrationFud…

…ge`.

As we said we'd do (in a recent commit that removed
`$FlowMigrationFudge`) as soon as `$FlowIgnore` became available.

Well, it's available now: the recent upgrade to Flow v0.128 brought
us facebook/flow@ba78ab9bf, which adds `$FlowIgnore` to the
standard/acceptable suppression syntax.

src/boot/store.js

@@ -173,7 +173,7 @@ const migrations: {| [string]: (GlobalState) => GlobalState |} = {
     ...state,
     accounts: state.accounts.map(a => ({
       ...a,
-      /* $FlowFixMe[prop-missing]: `a.realm` is a string until
+      /* $FlowIgnore[prop-missing]: `a.realm` is a string until
          migration 15 */
       realm: a.realm.replace(/\/+$/, ''),
     })),
@@ -211,7 +211,7 @@ const migrations: {| [string]: (GlobalState) => GlobalState |} = {
     ...state,
     accounts: state.accounts.map(a => ({
       ...a,
-      /* $FlowFixMe[incompatible-call]: `a.realm` will be a string
+      /* $FlowIgnore[incompatible-call]: `a.realm` will be a string
          here */
       realm: new URL(a.realm),
     })),

src/redux-persist-migrate/index.js

@@ -75,9 +75,9 @@ export function createMigrationImpl(
       throw new Error('createMigration: bad arguments');
     }
     if (action.type === REHYDRATE) {
-      // $FlowFixMe[prop-missing]
-      // $FlowFixMe[incompatible-exact]
-      /* $FlowFixMe[incompatible-type]
+      // $FlowIgnore[prop-missing]
+      // $FlowIgnore[incompatible-exact]
+      /* $FlowIgnore[incompatible-type]
          this really is a lie -- and kind of central to migration */
       const incomingState: State = action.payload;
       const incomingVersion = parseInt(versionSelector(incomingState), 10);