fix: Const argument of operator is not considered a variable

[AayushSabharwal]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[github-actions]

Benchmark Results (Julia vlts)

Time benchmarks

	master	22e3982...	master / 22e3982...
ODEProblem	4.31 ± 0.19 ms	4.45 ± 0.3 ms	0.969 ± 0.077
init	0.0436 ± 0.017 ms	0.0475 ± 0.018 ms	0.918 ± 0.49
large_parameter_init/ODEProblem	18.5 ± 2.2 ms	18.8 ± 2.2 ms	0.984 ± 0.16
large_parameter_init/init	0.0798 ± 0.027 ms	0.0747 ± 0.026 ms	1.07 ± 0.52
mtkcompile	6.95 ± 0.35 ms	7.07 ± 0.42 ms	0.983 ± 0.076
sparse_analytical_jacobian/ODEProblem	18 ± 1.1 ms	19 ± 1.1 ms	0.948 ± 0.079
sparse_analytical_jacobian/f_iip	0.053 ± 0.001 μs	0.053 ± 0.001 μs	1 ± 0.027
sparse_analytical_jacobian/f_oop	0.297 ± 0.0078 ms	0.297 ± 0.011 ms	1 ± 0.044
time_to_load	5.28 ± 0.06 s	5.18 ± 0.07 s	1.02 ± 0.018

Memory benchmarks

	master	22e3982...	master / 22e3982...
ODEProblem	0.0379 M allocs: 1.91 MB	0.0379 M allocs: 1.89 MB	1.01
init	0.417 k allocs: 0.0698 MB	0.417 k allocs: 0.0698 MB	1
large_parameter_init/ODEProblem	0.324 M allocs: 11.3 MB	0.324 M allocs: 11.3 MB	1
large_parameter_init/init	0.605 k allocs: 0.172 MB	0.605 k allocs: 0.172 MB	1
mtkcompile	0.0621 M allocs: 3.37 MB	0.0621 M allocs: 3.37 MB	1
sparse_analytical_jacobian/ODEProblem	0.19 M allocs: 7.82 MB	0.19 M allocs: 7.82 MB	1
sparse_analytical_jacobian/f_iip	0 allocs: 0 B	0 allocs: 0 B
sparse_analytical_jacobian/f_oop	0.634 k allocs: 19.6 kB	0.634 k allocs: 19.6 kB	1
time_to_load	0.153 k allocs: 14.5 kB	0.153 k allocs: 14.5 kB	1

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	22e3982...	master / 22e3982...
ODEProblem	3.99 ± 0.2 ms	3.99 ± 0.28 ms	1 ± 0.086
init	31.1 ± 10 μs	31.2 ± 10 μs	0.998 ± 0.46
large_parameter_init/ODEProblem	18.5 ± 2.3 ms	19.2 ± 1.7 ms	0.963 ± 0.15
large_parameter_init/init	0.0562 ± 0.017 ms	0.0553 ± 0.017 ms	1.02 ± 0.44
mtkcompile	5.95 ± 0.21 ms	5.91 ± 0.21 ms	1.01 ± 0.05
sparse_analytical_jacobian/ODEProblem	16.6 ± 2.1 ms	14.9 ± 1.2 ms	1.12 ± 0.17
sparse_analytical_jacobian/f_iip	0.055 ± 0.001 μs	0.064 ± 0.001 μs	0.859 ± 0.021
sparse_analytical_jacobian/f_oop	0.084 ± 0.011 ms	0.0809 ± 0.0055 ms	1.04 ± 0.15
time_to_load	5.36 ± 0.066 s	5.34 ± 0.085 s	1 ± 0.02

Memory benchmarks

	master	22e3982...	master / 22e3982...
ODEProblem	0.038 M allocs: 1.7 MB	0.038 M allocs: 1.71 MB	0.992
init	0.416 k allocs: 0.0518 MB	0.416 k allocs: 0.0518 MB	1
large_parameter_init/ODEProblem	0.35 M allocs: 12.6 MB	0.35 M allocs: 12.6 MB	1
large_parameter_init/init	0.799 k allocs: 0.152 MB	0.799 k allocs: 0.152 MB	1
mtkcompile	0.0601 M allocs: 2.68 MB	0.0601 M allocs: 2.68 MB	1
sparse_analytical_jacobian/ODEProblem	0.185 M allocs: 6.88 MB	0.185 M allocs: 6.89 MB	0.999
sparse_analytical_jacobian/f_iip	0 allocs: 0 B	0 allocs: 0 B
sparse_analytical_jacobian/f_oop	0.848 k allocs: 27 kB	0.848 k allocs: 27 kB	1
time_to_load	0.149 k allocs: 11.1 kB	0.149 k allocs: 11.1 kB	1