Pull Request Template

Description

Unhelpful exception thrown when incorrect browser is specified.

Doc updated as below

[x] The code change is covered by unit tests. I have added tests that prove my fix is effective or that my feature works
[x] I have performed end-to-end test locally.
[x] New and existing unit tests pass locally with my changes
[x] I have made corresponding changes to the documentation
[x] My changes generate no new warnings
[x] I used clear names for everything
[x] I have performed a self-review of my own code

Package	Line Rate	Branch Rate	Complexity	Health
Microsoft.PowerApps.TestEngine	94%	91%	830	✔
Summary	94% (2204 / 2339)	91% (527 / 578)	830	✔