tests: delete pointless assert

size_t is an unsigned type, therefore the comparison is always true.

Change-Id: I851fa0d59569ebc8e2572b1938020aadabb05f27
diff --git a/tests/test-common.hpp b/tests/test-common.hpp
index f5a309a..7c9c60d 100644
--- a/tests/test-common.hpp
+++ b/tests/test-common.hpp
@@ -88,8 +88,6 @@
   void
   advanceClocks(const time::nanoseconds& tick, size_t nTicks = 1)
   {
-    BOOST_ASSERT(nTicks >= 0);
-
     this->advanceClocks(tick, tick * nTicks);
   }