Remove RHist

It was removed in root-project/root#18191
and prevents compilation.

Author: jmcarcell

root/hist/hist/CMakeLists.txt

@@ -16,9 +16,3 @@ RB_ADD_GBENCHMARK(THistBenchmarks
    LABEL short
    LIBRARIES Hist Core)
 
-if(ROOT_root7_FOUND)
-RB_ADD_GBENCHMARK(RHistBenchmarks
-   RHistFillBenchmarks.cxx
-   LABEL short
-   LIBRARIES ROOTHist Core)
-endif()