Apply suggestions from SonarQube (#2340)

src/crypto/algorithms/olm.ts

@@ -70,7 +70,7 @@ class OlmEncryption extends EncryptionAlgorithm {
             return Promise.resolve();
         }
 
-        this.prepPromise = this.crypto.downloadKeys(roomMembers).then((res) => {
+        this.prepPromise = this.crypto.downloadKeys(roomMembers).then(() => {
             return this.crypto.ensureOlmSessionsForUsers(roomMembers);
         }).then(() => {
             this.sessionPrepared = true;
@@ -144,7 +144,7 @@ class OlmEncryption extends EncryptionAlgorithm {
             }
         }
 
-        return await Promise.all(promises).then(() => encryptedContent);
+        return Promise.all(promises).then(() => encryptedContent);
     }
 }
 
@@ -261,7 +261,7 @@ class OlmDecryption extends DecryptionAlgorithm {
      *
      * @return {string} payload, if decrypted successfully.
      */
-    private async decryptMessage(theirDeviceIdentityKey: string, message: IMessage): Promise<string> {
+    private decryptMessage(theirDeviceIdentityKey: string, message: IMessage): Promise<string> {
         // This is a wrapper that serialises decryptions of prekey messages, because
         // otherwise we race between deciding we have no active sessions for the message
         // and creating a new one, which we can only do once because it removes the OTK.
@@ -274,7 +274,7 @@ class OlmDecryption extends DecryptionAlgorithm {
             });
             // we want the error, but don't propagate it to the next decryption
             this.olmDevice.olmPrekeyPromise = myPromise.catch(() => {});
-            return await myPromise;
+            return myPromise;
         }
     }