remove forward-looking usages from the FileRef javadoc

Author: ThoSap

operator/src/main/java/it/aboutbits/postgresql/core/FileRef.java

@@ -10,14 +10,6 @@
 ///
 /// This class is used wherever a CRD spec needs to point to a specific file
 /// The [#path] field identifies the file location within the container.
-///
-/// ### Example usage in a CR manifest
-///
-/// ```yaml
-///  spec:
-///     adminSecretFileRef:
-///         path: "/mnt/secrets/db-credentials.json"
-/// ```
 @Getter
 @Setter
 @NullMarked