Fix single-server sending messeages when calling app back via notifications

[Zeromax]

This should fix the Issue described in #3136

Proposed changes

In order while researching the problem from #3136 I found out that the launch mode on master was set different. Setting the launch mode to singleTask as on master, everything works like expected

Tested on Android 11 Pixel 4 and Samsung Galaxy A52

Issue(s)

How to test or reproduce

1. create a Apk from this branch
2. Install it
3. login as a user A
4. check that notifications are working
5. move Rocket chat into background
6. send a message from an other user B
7. open rocket chat with clicking on the notification
8. send a message: Sending runs smooth withour error
9. Sending messages from other channels also works

Screenshots

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

[diegolmello]

LGTM

[diegolmello]

@Zeromax Thanks for your contribution :)