Fix the layout issue in the donation message

[ackintosh]

Issue Addressed

The emoji might not render correctly for some users. I saw that a user complained about the following layout issue in the donation message on social media. I believe he is a Windows user.

This PR removes the emoji from the message and replaces it with some text. The message looks like:

I know that some of ***Codegen classes implement their own donation message, but I have fixed DefaultCodegen only because of my limited bandwidth. 🙇

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
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  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
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[wing328]

I know that some of ***Codegen classes implement their own donation message, but I have fixed DefaultCodegen only because of my limited bandwidth. 🙇

We'll take care of the rest based on your fix 👍