docs: don't say that data flow tracing interface is unstable

We are starting to use data flow tracing in kernel.
The interface is not subject to change anymore.

Reviewed in https://reviews.llvm.org/D37303



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@312232 91177308-0d34-0410-b5e6-96231b3b80d8

docs/SanitizerCoverage.rst

@@ -281,8 +281,6 @@ the `LLVM GEP instructions <http://llvm.org/docs/GetElementPtr.html>`_
   // for every non-constant array index.
   void __sanitizer_cov_trace_gep(uintptr_t Idx);
 
-This interface is a subject to change.
-
 Default implementation
 ======================