Fix incorrect escaping in plotting files

Created by: Zaharid

One thing I didn't know is that there is a difference between single and double quotes in YAML:

https://stackoverflow.com/questions/32991517/how-to-escape-colons-and-other-special-characters-in-a-yaml-string

this is relevant when we use latex labels. For example something like:

dataset_label: "CMS $t\\bar{t}$  rapidity $y_{t\bar{t}}$"

parses like:

{'dataset_label': 'CMS $t\\bar{t}$ rapidity $y_{t\x08ar{t}}$'}

so with some non printable characters, that are also not valid latex. We should make sure that dataset_label is always escaped with single quotes and mention that in the relevant part of the guide.