Allow user to change MATCH_PASSWORD using match change_password when using S3 as storage mode

[damon02]

For match you need to supply a MATCH_PASSWORD. For Mac OS this is stored in the local keychain. If you use Git, it will be saved as a git repo specific match password, but with S3 there is only password called match_ inside the keychain.

Inside the documentation https://docs.fastlane.tools/actions/match/#passphrase it says that it only applies for Git storage, but the reality is that for S3 storage (and assume Google Cloud as well) it is also encrypting files using this password and will ask the first time.

If this value needs to be changed, for example if it is leaked, you will have to do it manually inside the keychain, and cannot use the fastlane match change_password command.

If you do try it you will be met by this:

% bundle exec fastlane match change_password
[✔] 🚀 
[00:00:00]: Successfully loaded './repo/fastlane/Matchfile' 📄

+-----------------+---------------------------+
| Detected Values from './fastlane/Matchfile' |
+-----------------+---------------------------+
| s3_bucket       | [REDACTED]                |
| s3_region       | [REDACTED]                |
| storage_mode    | s3                        |
| app_identifier  | [REDACTED]                |
+-----------------+---------------------------+

[!] Only git-based match allows you to change your password, current `storage_mode` is s3.

The error message gives the idea that you cannot change this password at all which is not true. It is not very intuitive and I would expect the change_password command to also be able to access this property inside the keychain since match was able to create it.

The documentation should be amended to include that the Passphrase is also being used for S3 storage (and Google cloud?). This will prevent some confusion in case users have to change it, and cannot do so using the command asking themselves if the passphrase is being used at all, which it is.