[striptags] remove typings from DT

[xavdid]

Please fill in this template.

• Use a meaningful title for the pull request. Include the name of the package modified.
• Test the change in your own code. (Compile and run.)
• Follow the advice from the readme.
• Avoid common mistakes.
• Run npm run lint package-name (or tsc if no tslint.json is present).

If removing a declaration:

• If a package was never on DefinitelyTyped, you don't need to do anything. (If you wrote a package and provided types, you don't need to register it with us.)
• Delete the package's directory.
• Add it to notNeededPackages.json.

[typescript-bot]

This PR has been open and unchanged 5 days without signoff or complaint. This will be merged by a maintainer soon if there are no objections.