chore(html): use const, format code example

[bsmth]

Fixes mdn/content#25750 :

I expected the github link to display the same code that is in the snippet below the code, or vice versa. They should match.

See https://developer.mozilla.org/en-US/docs/Learn/HTML/Introduction_to_HTML/Advanced_text_formatting#representing_computer_code

[dipikabh]

This example in https://github.com/mdn/learning-area/blob/main/html/introduction-to-html/advanced-text-formatting/other-semantics.html is still different from the one under "Representing computer code".

Perhaps we should also edit the "Representing computer code" section in mdn/content to break up this sentence:

Let's look at a few examples. You should try having a play with these (try grabbing a copy of our other-semantics.html sample file):

This line "You should try having a play with these (try grabbing a copy of our other-semantics.html sample file)" can be moved to after the result frame and probably changed to something like "You can try out these elements yourself. Grab a copy of another example in our other-semantics.html file)" so that it doesnt give the impression that it is the same example.

[bsmth]

Very good. I will follow up in content with a clarification it's not the entire file. Thank you!