Unable to release if change log contains 'Ù'

If the change log contains `ÙTF-8` instead of `UTF-8` the GitHub release fails with the error

```
ERROR: {"message":"Problems parsing JSON","documentation_url":"https://developer.github.com/v3/repos/releases/#create-a-release"}
At /Users/johlju/source/xFailOverCluster/output/RequiredModules/Sampler/0.99.0/tasks/GitHubRelease.functions.ps1:71 char:17
```

We should remove any invalid characters here, or throw an error saying that invalid characters was detected, and have the changelog HQRM QA test check for this.

https://github.com/gaelcolas/Sampler/blob/dee451c8ce1f925d36e344aa663624618d811e4e/.build/tasks/GitHubRelease.functions.ps1#L64

Start in .build/tasks/GitHubRelease.functions.ps1 around line 64, where the GitHub release data is prepared, and reproduce the failure with a changelog containing `ÙTF-8`. Review the changelog HQRM QA test mentioned in the issue. Done means invalid characters are handled as agreed and the QA test covers this case.

Written by the indexing model from the issue text.