yuzu/applets/software_keyboard: Override accept() and reject() instead of providing own differently named member functions

Uses Qt's built-in interface instead of rolling our own separate one on
top of it. This also fixes a bug in reject() where we were calling
accept() instead of reject().

src/yuzu/applets/software_keyboard.h

@@ -33,8 +33,8 @@ public:
                              Core::Frontend::SoftwareKeyboardParameters parameters);
     ~QtSoftwareKeyboardDialog() override;
 
-    void Submit();
-    void Reject();
+    void accept() override;
+    void reject() override;
 
     std::u16string GetText() const;
     bool GetStatus() const;