fix(src): updated to compile on gcc and clang

gcc disallows some constexprs that work in clang, these have been removed to that SERiF compiles on gcc and clang

src/composition/private/composition.cpp

@@ -357,7 +357,7 @@ namespace serif::composition {
             for (const auto& mass_fraction : mass_fractions) {
                 sum += mass_fraction;
             }
-            for (int i = 0; i < mass_fractions.size(); ++i) {
+            for (int i = 0; i < static_cast<int>(mass_fractions.size()); ++i) {
                 mass_fractions[i] /= sum;
             }
             for (auto& [symbol, entry] : m_compositions) {
@@ -594,10 +594,10 @@ namespace serif::composition {
             throw std::runtime_error("Composition has not been finalized (Consider running .finalize()).");
         }
         CanonicalComposition canonicalComposition;
-        constexpr std::array<std::string, 7> canonicalH = {
+        const std::array<std::string, 7> canonicalH = {
             "H-1", "H-2", "H-3", "H-4", "H-5", "H-6", "H-7"
         };
-        constexpr std::array<std::string, 8> canonicalHe = {
+        const std::array<std::string, 8> canonicalHe = {
             "He-3", "He-4", "He-5", "He-6", "He-7", "He-8", "He-9", "He-10"
         };
         for (const auto& symbol : canonicalH) {

src/eos/public/EOS.h

@@ -148,12 +148,6 @@ namespace serif::eos {
          */
         double specificHeatCapacityAtConstantPressure();
 
-        /**
-         * @brief Returns the format of the EOS data used to generate this output.
-         * @return The EOSFormat enum value (currently only EOSFormat::HELM).
-         */
-        EOSFormat EOSFormat() const;
-
         friend std::ostream& operator<<(std::ostream& os, const EOSOutput& output) {
             os << "EOSOutput:\n"
                 << "\tElectron Fraction: " << output.electronFraction << "\n"