debian/control: Add missing Build-Requires libosmo-simtrace2

In Change-Id Idf5a861f4dacbec3c664f4ced6e03d8662c73112 we introduced
the use of libosmo-simtrace2 (from simtrace2.git).  Our configure
script checks for it properly, but the debian/control wasn't updated.

Change-Id: I875f9d6d06d806fb9f9264840a65934fb0e99972

debian/control

@@ -12,6 +12,7 @@ Build-Depends: debhelper (>= 9),
                libcsv-dev,
                libosmocore-dev,
                libosmo-abis-dev,
+               libosmo-simtrace2,
                libpcsclite-dev,
                libusb-1.0-0-dev,
                libulfius-dev,