Remove subject filtering, keep only priority buttons

- Remove subject filter menu and related code
- Simplify filtering to priority groups only
- Keep Remove Filters button for priority reset
- Clean up unused code and UI elements

gotify_tray/gui/designs/widget_main.py

@@ -77,9 +77,6 @@ class Ui_MainWindow(object):
         self.label_subject = QtWidgets.QLabel(parent=self.verticalLayoutWidget)
         self.label_subject.setObjectName("label_subject")
         self.filtersLayout.addWidget(self.label_subject)
-        self.pb_subject = QtWidgets.QPushButton(parent=self.verticalLayoutWidget)
-        self.pb_subject.setObjectName("pb_subject")
-        self.filtersLayout.addWidget(self.pb_subject)
         self.pb_remove_filters = QtWidgets.QPushButton(parent=self.verticalLayoutWidget)
         self.pb_remove_filters.setObjectName("pb_remove_filters")
         self.filtersLayout.addWidget(self.pb_remove_filters)
@@ -109,7 +106,6 @@ class Ui_MainWindow(object):
         self.pb_high.setText(_translate("MainWindow", "HIGH"))
         self.pb_critical.setText(_translate("MainWindow", "CRITICAL"))
         self.label_subject.setText(_translate("MainWindow", "Subject:"))
-        self.pb_subject.setText(_translate("MainWindow", "Subject"))
         self.pb_remove_filters.setText(_translate("MainWindow", "Remove Filters"))