Merge bitcoin#16330: docs: Use placeholder instead of key expiration date

88fd556 Use placeholder instead of key expiration date (Hennadii Stepanov)

Pull request description:

  Use a placeholder instead of the actual expiration date, so that the documentation doesn't require updating every time an expiry date changes.

ACKs for top commit:
  fanquake:
    ACK 88fd556

Tree-SHA512: 391707833cc0e701cf560ec82fd91368468c90a95f85e4ce2a211b20d12463c85775142f28a3536b57c5f6950b9e6e0785632f6f071fa2180bc8aab53008603b

Author: fanquake

contrib/verifybinaries/README.md

@@ -6,7 +6,7 @@ Make sure you obtain the proper release signing key and verify the fingerprint w
 
 ```sh
 $ gpg --fingerprint "Bitcoin Core binary release signing key"
-pub   4096R/36C2E964 2015-06-24 [expires: 2017-02-13]
+pub   4096R/36C2E964 2015-06-24 [expires: YYYY-MM-DD]
       Key fingerprint = 01EA 5486 DE18 A882 D4C2  6845 90C8 019E 36C2 E964
 uid                  Wladimir J. van der Laan (Bitcoin Core binary release signing key) <[email protected]>
 ```