Fix Retry strategy ShouldHandle in example code

[marcrocny]

Pull Request

The issue or feature being addressed

The existing example compiles, but incorrectly shows the ShouldHandle delegate as operating on an Exception object.

Details on the issue fix or feature implementation

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• N/A, doc only I have included unit tests for the issue/feature
• N/A, doc only I have successfully run a local build

[marcrocny]

@dotnet-policy-service agree

[martincostello]

Thanks for the PR.

You'll need to change the code in the Snippets, which are used to generate the docs, otherwise the changes will get overwritten.

Once you've done that the docs can be regenerated with:

dotnet tool restore
dotnet mdsnippets