The copy button on install copies an extensive comman including env activation

### Describe the issue linked to the documentation

https://scikit-learn.org/stable/install.html

Above link will lead you to the sklearn downlanding for link . 
when you link copy link button it will copy 
`python3 -m venv sklearn-venvpython -m venv sklearn-venvpython -m venv sklearn-venvsource sklearn-venv/bin/activatesource sklearn-venv/bin/activatesklearn-venv\Scripts\activatepip install -U scikit-learnpip install -U scikit-learnpip install -U scikit-learnpip3 install -U scikit-learnconda create -n sklearn-env -c conda-forge scikit-learnconda activate sklearn-env`

instead of  `pip3 install -U scikit-learn`

if this is the issue so please issue i want to create a pull request for it and tell in which file this issue reside
Thanks

### Suggest a potential alternative/fix

By resoving above issue

COMMENT:
I think what happens is that the copy button selects all the text inside a `<code>` (or `<pre>`) tag, not just the visible text. One way that might fix this is to "invert" the following (and other occurrences):
```html
<div class="highlight"><pre><code
        ><span class="sk-expandable" data-packager="pip" data-os="linux" data-venv="">python3 -m venv sklearn-venv</span
        ><span class="sk-expandable" data-packager="pip" data-os="windows" data-venv="">python -m venv sklearn-venv</span
        ><span class="sk-expandable" data-packager="pip" data-os="mac" data-venv="">python -m venv sklearn-venv</span
        ><span class="sk-expandable" data-packager="pip" data-os="linux" data-venv="">source sklearn-venv/bin/activate</span
        ><span class="sk-expandable" data-packager="pip" data-os="mac" data-venv="">source sklearn-venv/bin/activate</span
        ><span class="sk-expandable" data-packager="pip" data-os="windows" data-venv="">sklearn-venv\Scripts\activate</span
        ><span class="sk-expandable" data-packager="pip" data-venv="">pip install -U scikit-learn</span
        ><span class="sk-expandable" data-packager="pip" data-os="mac" data-venv="no">pip install -U scikit-learn</span
        ><span class="sk-expandable" data-packager="pip" data-os="windows" data-venv="no">pip install -U scikit-learn</span
        ><span class="sk-expandable" data-packager="pip" data-os="linux" data-venv="no">pip3 install -U scikit-learn</span
        ><span class="sk-expandable" data-packager="conda">conda create -n sklearn-env -c conda-forge scikit-learn</span
        ><span class="sk-expandable" data-packager="conda">conda activate sklearn-env</span
       ></code></pre></div>
```

to:
```html
<div class="highlight">
<pre class="sk-expandable" data-packager="pip" data-os="linux" data-venv=""><code>
  <span>python3 -m venv sklearn-venv</span>
</pre></code>
<pre class="sk-expandable" data-packager="pip" data-os="windows" data-venv=""><code>
  <span >python -m venv sklearn-venv</span>
</pre></code>
... etc ...
</div>
```

so that we have one `<code>` per OS, instead of one `<code>` for all different OSs.

A related thought: how should one write these kinds of "changing text" so that screenreaders understand what is happening? Maybe by fixing that we also fix the copy button?

Labels: Documentation