Use GTK compat function with WEBVIEW_HINT_FIXED (#1322)

gtk_widget_set_size_request() was called when WEBVIEW_HINT_FIXED was
passed into webview_set_size(). That function is meant to set a minimum
size.

Instead we can call gtk_window_set_default_size() (GTK 4) or
gtk_window_resize() (GTK 3).

Author: SteffenL

core/include/webview/detail/backends/gtk_webkitgtk.hh

@@ -182,9 +182,9 @@ protected:
 
   noresult set_size_impl(int width, int height, webview_hint_t hints) override {
     gtk_window_set_resizable(GTK_WINDOW(m_window), hints != WEBVIEW_HINT_FIXED);
-    if (hints == WEBVIEW_HINT_NONE) {
+    if (hints == WEBVIEW_HINT_NONE || hints == WEBVIEW_HINT_FIXED) {
       gtk_compat::window_set_size(GTK_WINDOW(m_window), width, height);
-    } else if (hints == WEBVIEW_HINT_FIXED || hints == WEBVIEW_HINT_MIN) {
+    } else if (hints == WEBVIEW_HINT_MIN) {
       gtk_widget_set_size_request(m_window, width, height);
     } else if (hints == WEBVIEW_HINT_MAX) {
       gtk_compat::window_set_max_size(GTK_WINDOW(m_window), width, height);