Avoid useless FDuration cast in benchmark analysis (#2823)

Co-authored-by: Sven Johannsen <s.johannsen@bretgeld-engineering.de>

src/catch2/benchmark/detail/catch_analyse.cpp

@@ -63,8 +63,8 @@ namespace Catch {
                     FDuration mean = FDuration(0);
                     int i = 0;
                     for (auto it = first; it < last; ++it, ++i) {
-                        samples.push_back(FDuration(*it));
-                        mean += FDuration(*it);
+                        samples.push_back(*it);
+                        mean += *it;
                     }
                     mean /= i;