lint: reenable tslint arrow-return-shorthand, fix

src/providers/persistence/persistence.ts

@@ -338,8 +338,8 @@ export class PersistenceProvider {
 
   removeAllWalletData(walletId: string): Promise<void> {
     return this.clearLastAddress(walletId)
-      .then(() => { return this.removeTxHistory(walletId); })
-      .then(() => { return this.clearBackupFlag(walletId); });
+      .then(() => this.removeTxHistory(walletId))
+      .then(() => this.clearBackupFlag(walletId));
   };
 
   setAmazonGiftCards(network: string, gcs: any): Promise<void> {

tslint.json

@@ -31,7 +31,6 @@
     "no-string-literal": false,
     "no-var-keyword": false,
     "curly": false,
-    "member-access": false,
-    "arrow-return-shorthand": false
+    "member-access": false
   }
 }