Replace vague 'may not' with definitive 'will not'

This vagueness of 'may' has caused a great deal of confusion.
See https://stackoverflow.com/questions/8887318

PR-URL: nodejs/node#23143
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/modules.md

@@ -200,10 +200,11 @@ Modules are cached after the first time they are loaded. This means
 (among other things) that every call to `require('foo')` will get
 exactly the same object returned, if it would resolve to the same file.
 
-Multiple calls to `require('foo')` may not cause the module code to be
-executed multiple times.  This is an important feature. With it,
-"partially done" objects can be returned, thus allowing transitive
-dependencies to be loaded even when they would cause cycles.
+Provided `require.cache` is not modified, multiple calls to
+`require('foo')` will not cause the module code to be executed multiple times.
+This is an important feature. With it, "partially done" objects can be returned,
+thus allowing transitive dependencies to be loaded even when they would cause
+cycles.
 
 To have a module execute code multiple times, export a function, and call
 that function.