Update docs for 0.17

[elpiel]

Documentation issue

Summary

The documentation still mentions v16 and I've noticed that built-in shortcodes have been removed.
This is reflected in the Changelog (which I missed initially) but the docs still mention that there are built-in shortcodes

See second sentences of https://www.getzola.org/documentation/content/shortcodes/

Proposed solution

• Update version in docs to 0.17.1
• Remove mention of built-in shortcodes