chore: doc to use specific LZA version

Author: oliviergaumond

src/mkdocs/docs/lza-upgrade/faq.md

@@ -85,3 +85,14 @@ ORDER BY
 ```
 
 For more information about LZA related Quotas, refer to the [LZA Documentation about Quotas](https://docs.aws.amazon.com/solutions/latest/landing-zone-accelerator-on-aws/quotas.html) as well as this note about [CodeBuild concurrency](https://docs.aws.amazon.com/solutions/latest/landing-zone-accelerator-on-aws/prerequisites.html#update-codebuild-conncurrency-quota)
+
+## What version of LZA will be installed?
+
+By default, the LZA upgrade tools install the latest LZA official release. To specify a version to use, follow these instructions:
+
+1. Run `yarn migration-config` from the [Preparation phase](./preparation/prereq-config/#configuration)
+2. Edit the `src/input-config/input-config.json` file
+3. Add the following property to the file to specify which branch to use: `"lzaCodeRepositoryBranch": "release/v1.12.6"`
+4. Follow the remaining steps of the upgrade. This configuration will be used when you install LZA using the `yarn run lza-prep` command in the [Upgrade phase](./upgrade/install-lza.md)
+
+**Note:** If you are upgrading Non-Production and Production environments we recommend that you use the same version for both environments to replicate the same results. You can update to the latest LZA version once you upgraded from ASEA to LZA.

src/mkdocs/docs/lza-upgrade/preparation/prereq-config.md

@@ -96,6 +96,8 @@ yarn run migration-config
 !!! info
     By default the upgrade tool uses `ca-central-1` as the home region. If you use a different home region you need to set the AWS_REGION environment variable before running `migration-config`. e.g. `AWS_REGION=eu-west-1 yarn run migration-config`
 
+    By default the upgrade tool install the latest LZA official release. To specify a version to use see the [FAQ](../faq.md#what-version-of-lza-will-be-installed)
+
 ??? abstract "Detailed information"
     This command will also deploy a CloudFormation template and create two CodeCommit repositories. The CloudFormation template will create an S3 bucket for the resource mapping files. The first CodeCommit repository will also be used for the resource mapping files. The second CodeCommit repository will be used for the Landing Zone Accelerator configuration files that will be created in a later step.