qt dark style: fix padding of PayToEdit

based on Electron-Cash/Electron-Cash@7e69f0e6ea
see ColinDuquesnoy/QDarkStyleSheet#159

electrum/gui/qt/stylesheet_patcher.py

@@ -0,0 +1,18 @@
+"""This is used to patch the QApplication style sheet.
+It reads the current stylesheet, appends our modifications and sets the new stylesheet.
+"""
+
+from PyQt5 import QtWidgets
+
+
+def patch_qt_stylesheet(use_dark_theme: bool) -> None:
+    if not use_dark_theme:
+        return
+
+    app = QtWidgets.QApplication.instance()
+
+    style_sheet = app.styleSheet()
+    style_sheet = style_sheet + '''
+    QAbstractScrollArea { padding: 0px; }
+    '''
+    app.setStyleSheet(style_sheet)