docs(security): update deprecated method from @casl/ability

[usystemsoftwares]

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [X] Docs
• [ ] Other... Please describe:

What is the current behavior?

Warning message - "@deprecated use createMongoAbility function instead and MongoAbility interface. In the next major version PureAbility will be renamed to Ability and this class will be removed"

What is the new behavior?

Keep official documentation up to date!

Does this PR introduce a breaking change?

• [ ] Yes
• [X] No

Other information

Happy to be able to keep up to date the official documentation of this exceptional framework that is Nest.js.