keep clang happy even though I don't believe it's right

Clang complains that:
```
SOURCES/QualityControl/2660/0/Framework/test/testActor.cxx
/Volumes/build/alice-ci-workdir/qualitycontrol-o2/sw/SOURCES/QualityControl/2660/0/Framework/test/testActor.cxx:97:5: error: call to consteval function 'o2::quality_control::core::UnrequestedAccessActor::assertNoAccessToServices<o2::quality_control::core::UnrequestedAccessActor>' is not a constant expression
   97 |     assertNoAccessToServices<UnrequestedAccessActor>();
      |     ^
/Volumes/build/alice-ci-workdir/qualitycontrol-o2/sw/SOURCES/QualityControl/2660/0/Framework/test/testActor.cxx:97:5: note: implicit use of 'this' pointer is only allowed within the evaluation of a call to a 'constexpr' member function
1 error generated.
```

GCC is fine and is able to process it as a consteval expression. Let's keep both happy by using constexpr, given it's just a test.

Author: knopers8

Framework/test/testActor.cxx

@@ -84,7 +84,7 @@ class UnrequestedAccessActor : public Actor<UnrequestedAccessActor>
   explicit UnrequestedAccessActor(const ServicesConfig& cfg) : Actor<UnrequestedAccessActor>(cfg) {}
 
   template <typename T>
-  consteval void assertNoAccessToServices()
+  constexpr void assertNoAccessToServices()
   {
     static_assert(!(requires(T& t) { t.getMonitoring(); }));
     static_assert(!(requires(T& t) { t.getBookkeeping(); }));