Don't build a NUCLEO_F103RB release for now

NUCLEO_F103RB is not yet integrated in the on-line environment, so don't
build a release for it yet.

Author: Bogdan Marinescu

workspace_tools/build_release.py

@@ -34,7 +34,6 @@
     ('LPC1347', ('ARM',)),
     ('LPC4088', ('ARM', 'GCC_ARM', 'GCC_CR')),
     ('LPC1114', ('uARM',)),
-    ('NUCLEO_F103RB', ('ARM', 'uARM', 'GCC_ARM')),
 )