Remove recursive include (#5705)

Co-authored-by: Kim Kulling <[email protected]>

include/assimp/StringComparison.h

@@ -57,7 +57,6 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #pragma GCC system_header
 #endif
 
-#include <assimp/StringComparison.h>
 #include <assimp/ai_assert.h>
 #include <assimp/defs.h>