Remove unused variables in mapillary/opensfm/opensfm/src/foundation/n…

…ewton_raphson.h

Summary:
LLVM-15 has a warning `-Wunused-but-set-variable` which we treat as an error because it's so often diagnostic of a code issue. Unused variables can compromise readability or, worse, performance.

This diff either (a) removes an unused variable and, possibly, it's associated code, or (b) qualifies the variable with `[[maybe_unused]]`, mostly in cases where the variable _is_ used, but, eg, in an `assert` statement that isn't present in production code.

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Reviewed By: palmje

Differential Revision: D53779594

fbshipit-source-id: a22fbbc945140165686a74c9d0c921983ca54451

opensfm/src/foundation/newton_raphson.h

@@ -44,7 +44,6 @@ template <class F>
 struct FiniteDiff<F, 1, 1> {
   static typename TypeTraits<1, 1>::Jacobian Derivative(
       const F& func, typename TypeTraits<1, 1>::Values& x) {
-    typename TypeTraits<1, 1>::Jacobian jacobian;
     constexpr auto eps = 1e-15;
     return (func(x + eps) - func(x)) / eps;
   }
@@ -77,7 +76,6 @@ template <class F, int N, int M, class D = FiniteDiff<F, N, M>>
 typename TypeTraits<N, M>::Values NewtonRaphson(
     const F& func, const typename TypeTraits<N, M>::Values& initial_value,
     int iterations, double tol = 1e-6) {
-  constexpr auto eps = std::numeric_limits<double>::epsilon();
   auto current_value = initial_value;
   for (int i = 0; i < iterations; ++i) {
     const auto at_current_value = func(current_value);