doc: clarify description of readable.push() method

PR-URL: #29687
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/stream.md

@@ -2148,8 +2148,8 @@ class SourceWrapper extends Readable {
 }
 ```
 
-The `readable.push()` method is intended be called only by `Readable`
-implementers, and only from within the `readable._read()` method.
+The `readable.push()` method is used to push the content
+into the internal buffer. It can be driven by the `readable._read()` method.
 
 For streams not operating in object mode, if the `chunk` parameter of
 `readable.push()` is `undefined`, it will be treated as empty string or