doc: normalize JavaScript code block info strings

Prior to this commit, JavaScript fenced code blocks in Markdown files
had inconsistent info strings. This has been corrected to standardize
on the one with the highest frequency in the doc/api/ dir.

Stats:
>  'js' => 1091,
>  'javascript' => 2,

PR-URL: https://github.com/nodejs/node/pull/33531


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Zeyu Yang <himself65@outlook.com>