Merge bitcoin/bitcoin#27176: docs: GetDataDirNet and GetDataDirBase don't create datadir

fb0dbe9 docs: GetDataDirNet and GetDataDirBase don't create datadir (stickies-v)

Pull request description:

  Since #27073, the behaviour of `GetDataDir()` [changed](https://github.com/bitcoin/bitcoin/pull/27073/files#diff-19427b0dd1a791adc728c82e88f267751ba4f1c751e19262cac03cccd2822216L435-L443) to only return the datadir path, but not create it if non-existent. This also changed the behaviour of `GetDataDirNet()` and `GetDataDirBase()` but the docs do not yet reflect that.

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Tree-SHA512: 3f10f4871df59882f3649c6d3b2362cae2f8a01ad0bd0c636c5608b0d177d279a2e8712930b819d6d3912e91fa6447b9e54507c33d8afe427f7f39002b013bfb

Author: fanquake

src/util/system.h

@@ -287,15 +287,13 @@ class ArgsManager
      * Get data directory path
      *
      * @return Absolute path on success, otherwise an empty path when a non-directory path would be returned
-     * @post Returned directory path is created unless it is empty
      */
     const fs::path& GetDataDirBase() const { return GetDataDir(false); }
 
     /**
      * Get data directory path with appended network identifier
      *
      * @return Absolute path on success, otherwise an empty path when a non-directory path would be returned
-     * @post Returned directory path is created unless it is empty
      */
     const fs::path& GetDataDirNet() const { return GetDataDir(true); }