Change MariaDB example from Gen4 server to Gen5 server

[elemount]

MariaDB service does not support Gen4 server currently, so change its examples from Gen4 to Gen5.

PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• Except for special cases involving multiple contributors, the PR is started from a fork of the main repository, not a branch.
• If applicable, the PR references the bug/issue that it fixes.
• Swagger files are correctly named (e.g. the api-version in the path should match the api-version in the spec).

Quality of Swagger

• I have read the contribution guidelines.
• My spec meets the review criteria:
  • The spec conforms to the Swagger 2.0 specification.
  • The spec follows the guidelines described in the Swagger checklist document.
  • Validation tools were run on swagger spec(s) and have all been fixed in this PR.

[AutorestCI]

Automation for azure-sdk-for-python

Unable to detect any generation context from this PR.

[AutorestCI]

Automation for azure-sdk-for-js

Unable to detect any generation context from this PR.

[AutorestCI]

Automation for azure-sdk-for-java

Unable to detect any generation context from this PR.

[AutorestCI]

Automation for azure-sdk-for-ruby

Unable to detect any generation context from this PR.

[AutorestCI]

Automation for azure-sdk-for-node

Unable to detect any generation context from this PR.

[azuresdkci]

Can one of the admins verify this patch?

[AutorestCI]

Automation for azure-sdk-for-go

Unable to detect any generation context from this PR.