test: validate full error messages

test: changed test2 of test-vm-timeout.js so that entire error message
      would be matched in assert.throw.

      Before test 2 of test-vm-timeout.js would match any RangeError,
      now it looks specifically for the error message
      "RangeError: timeout must be a positive number"

test: changed test 3 of test-vm-timeout.js so that entire error message
      would be matched in assert.throw.

      Before test 3 of test-vm-timeout.js would match any RangeError,
      now it looks specifically for the error message
      "RangeError: timeout must be a positive number"

PR-URL: https://github.com/nodejs/node/pull/13453
Refs: https://github.com/nodejs/node/issues/13454


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>