Merge #15887: docs: Align code example style with clang-format

201393f932 Align code example with clang-format (Hennadii Stepanov)

Pull request description:

  With this PR running [clang-format-diff.py](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/clang-format-diff.py) on the code example will not fire a format adjustment.

ACKs for commit 201393:
  MarcoFalke:
    trivial ACK 201393f932

Tree-SHA512: 825c5e8cfba1bc140c2dfc38b82c5eec268b82b528af4301f25dfacc1f4f0788e268e72e8512f7ce001be665a8b07964a0af832fd9a1c6bd1c27d252f93619bc

doc/developer-notes.md

@@ -620,8 +620,8 @@ class AddressBookPage
     Mode m_mode;
 }
 
-AddressBookPage::AddressBookPage(Mode _mode) :
+AddressBookPage::AddressBookPage(Mode _mode)
-      m_mode(_mode)
+    : m_mode(_mode)
 ...
 ```