Clean up English in JSON documentation

[AdamLearns]

This change only improves the wording and grammar used on this page. I originally only wanted to fix a typo, but I ended up proof-reading the whole page, and at least one function should be clearer as a result.

Note that I did not update any translation files:

╰─❯ rg "enables all data"
doc/translations/zh_TW.po
50968:"The [JSON] enables all data types to be converted to and from a JSON string. "

doc/translations/zh_CN.po
68886:"The [JSON] enables all data types to be converted to and from a JSON string. "

...should something be done with those?

[Calinou]

Note that I did not update any translation files:
...should something be done with those?

You don't need to do anything here, since they are updated automatically by maintainers on a regular basis.

[AdamLearns]

Is there an easy way to see the resulting page that I've modified before committing? It didn't seem to be part of building Godot, and I wasn't positive based on the instructions here if I just need to look at individual pages using Sphinx/reST.

Sorry, this was answered as soon as I made the comment 🤦‍♂️: https://docs.godotengine.org/en/stable/contributing/documentation/building_the_manual.html

[mhilbrunner]

Thanks for contributing :) The commits need to be squashed into one before this can be merged. See here for one explanation on how to do do that.

Otherwise, the changes themselves look good to me.

[akien-mga]

Thanks!

[AdamLearns]

Ah, sorry, Tuesdays and Thursdays are my catch-up days, so I didn't have a chance to look at this until now. I see that it's already been merged though—thank you for including the work! 🙏