Cross product tools: Fix typos in help section

[RZ9082]

Fixing some typos in the help section of flat cross product and nested cross product tools,

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[bgruening]

Thanks @RZ9082!