Make notes conform to new style

[joaofnfernandes]

Follow-up of #2710. Now that have different css classes for notes and warnings, we should clean up existing notes to make them conform to the new style.

You can see an example of the new style at #2710

[shubheksha]

I'll try to work on this over the course of this week!

[shubheksha]

Should I wait for #2795 before working on this?

[mdlinville]

No, you can go ahead with this work, it is only the CSS we are discussing in #2795. The classes will be the same, so the method will be the same.

[clocklear]

@shubheksha are you still working on this? This issue hasn't been marked as claimed.

[tippexs]

claimed

[mdlinville]

@shubheksha had you intended to claim this or started work on it yet?

[shubheksha]

@mstanleyjones, yes I've started work on this.

[joaofnfernandes]

#2937 relates to this