fix: equality comparison where assignment was likely meant (#979)

Author: ForceBru

src/multivariate/solvers/constrained/ipnewton/ipnewton.jl

@@ -323,7 +323,7 @@ function update_state!(
     # Evaluate the constraints at the new position
     constraints.c!(state.constr_c, state.x)
     constraints.jacobian!(state.constr_J, state.x)
-    state.ev == equality_violation(constraints, state)
+    state.ev = equality_violation(constraints, state)
 
     false
 end