tools: increase the maximum number of files to lint per worker

This increases the maximum number of files to lint per worker from
40 to 60 files. This should ideally reduce the total linting time
a tiny bit.

PR-URL: https://github.com/nodejs/node/pull/27670


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>