doc: reword possessive form of Node.js in zlib.md

Throughout the docs, we sometimes write the possessive of _Node.js_ as
_Node.js'_ and other times as _Node.js's_. The former conforms with some
generally accepted style guides (e.g., Associated Press Stylebook) while
the latter complies with others (e.g., Chicago Manual of Style).

Since there is no clear authoritative answer as to which form is
correct, and since (at least to me) both are visually jarring and
sometimes cause a pause to understand, I'd like to reword things to
eliminate the possessive form where possible.

This is one of those examples.

PR-URL: #31713
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Beth Griggs <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

doc/api/zlib.md

@@ -174,7 +174,7 @@ decompressed result is valid.
 
 ### For zlib-based streams
 
-From `zlib/zconf.h`, modified to Node.js's usage:
+From `zlib/zconf.h`, modified for Node.js usage:
 
 The memory requirements for deflate are (in bytes):