Update URL demo in docs

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.12%. Comparing base (aa23363) to head (b84a7a8).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #677 +/- ## ======================================= Coverage 95.12% 95.12% ======================================= Files 79 79 Lines 3018 3018 ======================================= Hits 2871 2871 Misses 147 147 ``` | [Flag](https://app.codecov.io/gh/Terralego/TerraVisu/pull/677/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Terralego) | Coverage Δ | | |---|---|---| | [backend-unittests](https://app.codecov.io/gh/Terralego/TerraVisu/pull/677/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Terralego) | `95.12% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Terralego#carryforward-flags-in-the-pull-request-comment) to find out more.

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