Pin all plugins to latest major version

[github-actions[bot]]

Changes to whippet.lock detected. The following version changes will be applied:

--- /dev/fd/63  2024-08-07 16:31:20.536130152 +0000
+++ /dev/fd/62  2024-08-07 16:31:20.536130152 +0000
@@ -1,7 +1,7 @@
 {
     "plugins": {
-        "akismet": "v5.2",
-        "advanced-custom-fields-pro": "v6.3.2.1"
+        "akismet": "v5.3.3",
+        "advanced-custom-fields-pro": "v6.3.5"
     }
 }