fix: ignore flaky Raspberry Pi documentation URL

Agent-Logs-Url: https://github.com/Arm-Examples/.github/sessions/7b17b3d5-9056-4e7a-af40-1e559abdafb3

Co-authored-by: ReinhardKeil <8268058+ReinhardKeil@users.noreply.github.com>

Author: Copilot

.lycheeignore

@@ -4,4 +4,5 @@
 # Known false positive / environment-sensitive
 https://www.raspberrypi.com/software
 https://www.raspberrypi.com/software/
+https://www.raspberrypi.com/documentation/computers/getting-started.html#imager-install
 https://www.st.com/en/embedded-software/x-cube-stl.html