Developer guide: add clarification on copyright header (line#6295)

Author: schiemon

site/src/pages/community/developer-guide.mdx

@@ -103,6 +103,10 @@ License for the specific language governing permissions and limitations
 under the License.
 ```
 
+Please avoid introducing noise into your PRs by changing the date (`$today.year`) for every file you modify.
+In IntelliJ, make sure you
+[disable](https://www.jetbrains.com/help/idea/copyright.html#update-copyright-on-save) automatic copyright header updates.
+
 ## Add Javadoc
 
 All public classes and public or protected methods must have Javadoc,