Updated dataless docs

[ESadek-MO]

🚀 Pull Request

Description

---

Consult Iris pull request check list

---

Add any of the below labels to trigger actions on this PR:

• benchmark_this Request that this pull request be benchmarked to check if it introduces performance shifts
  Related to Make dataless cubes work with cube operations #6336

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.43%. Comparing base (bb0ef8c) to head (2b77ff6).
⚠️ Report is 48 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6866      +/-   ##
==========================================
+ Coverage   90.40%   90.43%   +0.02%     
==========================================
  Files          91       91              
  Lines       24833    24839       +6     
  Branches     4653     4656       +3     
==========================================
+ Hits        22451    22463      +12     
+ Misses       1612     1608       -4     
+ Partials      770      768       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ukmo-ccbunney]

All good 👍🏼