module: correct docs about when extensionless files are supported

PR-URL: nodejs#31415
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/api/esm.md

@@ -33,9 +33,9 @@ initial input, or when referenced by `import` statements within ES module code:
 
 * Files ending in `.mjs`.
 
-* Files ending in `.js`, or extensionless files, when the nearest parent
-  `package.json` file contains a top-level field `"type"` with a value of
-  `"module"`.
+* Files ending in `.js`, or extensionless files when run as main entry points on
+  the command line, when the nearest parent `package.json` file contains a
+  top-level field `"type"` with a value of `"module"`.
 
 * Strings passed in as an argument to `--eval` or `--print`, or piped to
   `node` via `STDIN`, with the flag `--input-type=module`.
@@ -50,9 +50,9 @@ or when referenced by `import` statements within ES module code:
 
 * Files ending in `.cjs`.
 
-* Files ending in `.js`, or extensionless files, when the nearest parent
-  `package.json` file contains a top-level field `"type"` with a value of
-  `"commonjs"`.
+* Files ending in `.js`, or extensionless files when run as main entry points on
+  the command line, when the nearest parent `package.json` file contains a
+  top-level field `"type"` with a value of `"commonjs"`.
 
 * Strings passed in as an argument to `--eval` or `--print`, or piped to
   `node` via `STDIN`, with the flag `--input-type=commonjs`.