Maintenance: Typo in Operator Splitting Example (#653)

Fix typo in error check

examples/arkode/C_serial/ark_analytic_partitioned.c

@@ -145,7 +145,7 @@ int main(int argc, char* argv[])
       }
 
       flag = SplittingStepSetCoefficients(arkode_mem, coefficients);
-      if (check_flag(&flag, "ARKodeSetFixedStep", 1)) { return 1; }
+      if (check_flag(&flag, "SplittingStepSetCoefficients", 1)) { return 1; }
 
       SplittingStepCoefficients_Destroy(&coefficients);
     }