doc: remove URLs from zlib docs

This commit removes two URLs from the zlib documentation. One
of the URLs is already linked to in the previous sentence, so
it is removed completely. The other is changed to more human
friendly link text.

PR-URL: #28580
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/api/zlib.md

@@ -258,8 +258,7 @@ All of the constants defined in `zlib.h` are also defined on
 `require('zlib').constants`. In the normal course of operations, it will not be
 necessary to use these constants. They are documented so that their presence is
 not surprising. This section is taken almost directly from the
-[zlib documentation][]. See <https://zlib.net/manual.html#Constants> for more
-details.
+[zlib documentation][].
 
 Previously, the constants were available directly from `require('zlib')`, for
 instance `zlib.Z_NO_FLUSH`. Accessing the constants directly from the module is
@@ -408,8 +407,8 @@ ignored by the decompression classes.
   empty dictionary by default)
 * `info` {boolean} (If `true`, returns an object with `buffer` and `engine`.)
 
-See the description of `deflateInit2` and `inflateInit2` at
-<https://zlib.net/manual.html#Advanced> for more information on these.
+See the [`deflateInit2` and `inflateInit2`][] documentation for more
+information.
 
 ## Class: BrotliOptions
 <!-- YAML
@@ -1039,6 +1038,7 @@ Decompress a chunk of data with [`Unzip`][].
 [`Inflate`]: #zlib_class_zlib_inflate
 [`TypedArray`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
 [`Unzip`]: #zlib_class_zlib_unzip
+[`deflateInit2` and `inflateInit2`]: https://zlib.net/manual.html#Advanced
 [`stream.Transform`]: stream.html#stream_class_stream_transform
 [`zlib.bytesWritten`]: #zlib_zlib_byteswritten
 [Brotli parameters]: #zlib_brotli_constants