Added coma in parameter list to avoid the following error when

using Ecne:

```

ERROR: LoadError: syntax: missing comma or ) in argument list
Stacktrace:
 [1] top-level scope
   @ ~/R1CSConstraintSolver.jl:659
 [2] include
   @ ./Base.jl:418 [inlined]
 [3] include_package_for_output(pkg::Base.PkgId, input::String, depot_path::Vector{String}, dl_load_path::Vector{String}, load_path::Vector{String}, concrete_deps::Vector{Pair{Base.PkgId, UInt64}}, source::String)
   @ Base ./loading.jl:1318
 [4] top-level scope
   @ none:1
 [5] eval
   @ ./boot.jl:373 [inlined]
 [6] eval(x::Expr)
   @ Base.MainInclude ./client.jl:453
 [7] top-level scope
   @ none:1

```

src/R1CSConstraintSolver.jl

@@ -655,7 +655,7 @@ function SolveConstraintsSymbolic(
     debug::Bool=false,
     target_variables::Vector{Int64}=[],
     num_variables::Int=-1,
-    input_sym::String="default.sym"
+    input_sym::String="default.sym",
     secp_solve::Bool=false,
 )
     num_unknowns =