C#: Fix CFG for assertion.

Author: aschackmull

csharp/ql/lib/semmle/code/csharp/controlflow/internal/Completion.qll

@@ -429,11 +429,6 @@ private predicate inBooleanContext(Expr e) {
   or
   e = any(SpecificCatchClause scc).getFilterClause()
   or
-  exists(BooleanAssertMethod m, int i |
-    assertion(_, i, m, e) and
-    i = m.getAnAssertionIndex(_)
-  )
-  or
   e = any(LogicalNotExpr lne | inBooleanContext(lne)).getAnOperand()
   or
   exists(LogicalAndExpr lae |