contrib: Disable doxygen doc generation

The --disable-doxygen was recently added to libosmocore and
libosmo-netif. No need to manually remove documentation anymore.

Change-Id: I3ca3dd1c115fc6784e4dc26a5ff5bf35d65b4e22
diff --git a/contrib/jenkins-build-osmo-bts-sysmo.sh b/contrib/jenkins-build-osmo-bts-sysmo.sh
index dad2151..f286368 100755
--- a/contrib/jenkins-build-osmo-bts-sysmo.sh
+++ b/contrib/jenkins-build-osmo-bts-sysmo.sh
@@ -16,7 +16,7 @@
 # for gsm_data_shared.h
 have_repo openbsc
 
-build_repo libosmocore --disable-pcsc
+build_repo libosmocore --disable-pcsc --disable-doxygen
 build_repo libosmo-abis
 build_repo osmo-bts --enable-sysmocom-bts --with-openbsc=$base/openbsc/openbsc/include