FindBoost.cmake: Fixes 11246

FindBoost can find shared libraries (.so) in rare circumstances
even when Boost_USE_STATIC_LIBS is set

Modules/FindBoost.cmake

@@ -800,7 +800,7 @@ ELSE (_boost_IN_CACHE)
     if(WIN32)
       set(CMAKE_FIND_LIBRARY_SUFFIXES .lib .a ${CMAKE_FIND_LIBRARY_SUFFIXES})
     else()
-      set(CMAKE_FIND_LIBRARY_SUFFIXES .a ${CMAKE_FIND_LIBRARY_SUFFIXES} )
+      set(CMAKE_FIND_LIBRARY_SUFFIXES .a )
     endif()
   endif()