Sankey: Remove duplicated examples

[nirname]

📑 Summary

It is not clear for me, which keyword I should use, so based on other pages I probably need to remove duplicates, because what I did initially was adding 2 blocks:

```mermaid
%% diagram
```

```mermaid-example
%% diagram
```

In my case when I develop docs, mermaid-example do not produce diagram at all, although it should be, probably

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 📓 have added documentation (if appropriate)
• 🔖 targeted develop branch

[nirname]

Guys, I cannot fully understand, how examples page works and how to use mermaid-example blocks.
Lets have a look at this one packages/mermaid/src/docs/intro/examples.md
I start docs:dev
When I update examples directly - nothing happens.
There is no code blocks called mermaid only mermaid-example and for local development it never displays a diagram, but in production it does.
If I add diagram to examples.md - nothing happens.
Diagram does not appear even when I update index.md.
Furthermore, I need to add a diagram in mermaid block to examples.md and the same type of diagram to index.md, and only then a diagram appears, but mermaid-example never emtis diagram. How does it work?

[codecov]

Codecov Report

Merging #4595 (9f5f0a6) into develop (f431bae) will decrease coverage by 0.30%.
The diff coverage is 100.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4595      +/-   ##
===========================================
- Coverage    80.12%   79.83%   -0.30%     
===========================================
  Files          143      143              
  Lines        16487    16487              
  Branches       518      518              
===========================================
- Hits         13210    13162      -48     
- Misses        3172     3220      +48     
  Partials       105      105              

Flag	Coverage Δ
e2e	83.95% <ø> (-0.47%)	⬇️
unit	58.12% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/mermaid/src/defaultConfig.ts	93.82% <100.00%> (ø)

... and 8 files with indirect coverage changes

[sidharthv96]

#4598 should resolve the issues with docs.