Bump webtesting rules and uses versioned browser for tests.

[arcra]

The bazel web testing rules package provides versioned browsers for testing, which should be easier for us to update/maintain than using additional rules to define our own browser.

The one from 0.3.3 was picked somewhat arbitrarily as it seems old enough to provide enough compatibility coverage, without being as old as the version we were using before.

This change might produce some scuba tests to be updated.

Alternatively, we can accomplish the same result we had before with our custom browser, but some of the rules that we use for this purpose have been removed/changed.

In that case, we'd need to use the platform_archive rule, like they do here, and then define a browser similarly like they do here, which in turn declares a dependency on this file, which is the one that references the output from the platform_archive rule.