Remove duplicate signup route

src/App.tsx

@@ -41,7 +41,6 @@ function App() {
               <Route path="/homeworks/register" element={<RegisterHomework />} />
               <Route path="/characters/:characterId/homeworks" element={<CharacterHomeworkSelect />} />
               <Route path="/dashboard" element={<Dashboard />} />
-              <Route path="/signup" element={<Signup />} />
               <Route path="/me" element={<MePage />} />
               <Route path="/characters/:id/edit" element={<CharacterEditPage />} />
               <Route path="/homeworks/:id/edit" element={<HomeworkEditPage />} />