Fix linkcheck

Added a 5 second timeout for links, and skipping one which often takes a
good long while seems to have linkcheck completing again, at least
locally.

QA: ran linkcheck

Jira issue: none

Signed-off-by: Katrina Prosise <katrina.prosise@foundries.io>

source/conf.py

@@ -135,8 +135,12 @@
     'https://mgmt.foundries.io/leshan/#/security',
     'https://github.com/foundriesio/fiotest#testing-specification',
     'https://github.com/foundriesio/jobserv/blob/72935348e902cdf318cfee6ab00acccee1438a7c/jobserv/notify.py#L141-L146',
+    'https://www.st.com/en/development-tools/stm32cubeprog.html', #slow, very slow.
 ]
 
+# Time in seconds to wait for a response. May result infalse errors, but also keeps things from timing out
+linkcheck_timeout = 5
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']