fix heading levels (#7906)

Co-authored-by: katiegoines <[email protected]>

Author: katieklein

src/fragments/lib/auth/common/mfa/add_mfa.mdx

@@ -1,4 +1,4 @@
-#### SMS MFA
+### SMS MFA
 ```bash
 $ amplify add auth
 
@@ -21,7 +21,7 @@ Some next steps:
 "amplify publish" will build all your local backend and frontend resources (if you have hosting category added) and provision it in the cloud
 ```
 
-#### TOTP MFA
+### TOTP MFA
 ```bash
 $ amplify add auth
 
@@ -40,4 +40,4 @@ $ amplify add auth
 Some next steps:
 "amplify push" will build all your local backend resources and provision it in the cloud
 "amplify publish" will build all your local backend and frontend resources (if you have hosting category added) and provision it in the cloud
-```
+```

src/fragments/lib/auth/common/mfa/update_mfa.mdx

@@ -3,7 +3,7 @@ The following steps show how to enable MFA as "Optional" for users. In this mode
 
 If you'd like to make MFA required for users, you must first delete your auth resource by running `amplify remove auth`, then follow the **New Project** flow on this page.
 
-#### SMS MFA
+### SMS MFA
 ```bash
 $ amplify update auth
 
@@ -27,7 +27,7 @@ Some next steps:
 ```
 
 
-#### TOTP MFA
+### TOTP MFA
 ```bash
 $ amplify update auth
 
@@ -46,4 +46,4 @@ $ amplify update auth
 Some next steps:
 "amplify push" will build all your local backend resources and provision it in the cloud
 "amplify publish" will build all your local backend and frontend resources (if you have hosting category added) and provision it in the cloud
-```
+```

src/pages/gen1/[platform]/build-a-backend/auth/manage-mfa/index.mdx

@@ -33,7 +33,7 @@ export function getStaticProps(context) {
 
 The Auth category supports Multi-factor Authentication (MFA) for user sign-in flows. MFA is an extra layer of security used to make sure that users trying to gain access to an account are who they say they are. It requires users to provide additional information to verify their identity. Amplify Auth supports the MFA methods with Time-based-One-Time Passwords (TOTP) as well as text messages (SMS). In this guide we will review how you can set up MFA using TOTP and SMS and the tradeoffs between these methods to help you choose the right set up for your application. We’ll also review how to set up MFA to remember a device and reduce sign-in friction for your users.
 
-Before you begin, you will need:
+Before you begin, you will need: 
 
 - The Amplify libraries installed and configured
 - _Optional_ If you are using SMS you will need a phone number provisioned with an [SNS/Pinpoint](https://docs.aws.amazon.com/sns/latest/dg/channels-sms-originating-identities.html)