Use SetMinimumSize in about dialog

src/dialogs/about.h

@@ -32,7 +32,6 @@
 #include "ui_about.h"
 
 class QWidget;
-class QShowEvent;
 
 class About : public QDialog {
   Q_OBJECT
@@ -40,9 +39,6 @@ class About : public QDialog {
  public:
   explicit About(QWidget *parent = nullptr);
 
- protected:
-  void showEvent(QShowEvent*);
-
  private:
   struct Person {
     Person(const QString &n, const QString &e = QString()) : name(n), email(e) {}