Add trimmed to all multilines blocktrans tags

[humitos]

Following what @ewjoachim said in #4471,

Now I think most of these problems are pretty much stemming from the usage of blocktrans without trimmed, and that makes the translation quite more complex to write. There are some other issues, though.

I updated all our templates to add trimmed to all multilines blocktrans tag.

This PR should be merged before #4478 I suppose, so we don't override the resources twice.

[humitos]

This PR was done by running these commands:

$ cd readthedocs/
$ find . -iname "*.html" -type f -exec sed -i -e 's/blocktrans trimmed/blocktrans/gi' {} \;        

$ find . -iname "*.html" -type f -exec sed -i -e 's/{% blocktrans/{% blocktrans trimmed/gi' {} \;

[ewjoachim]

This is 👌perfect. The .po file must be in a much better state now !

[ericholscher]

👍