fix minor bug in synth settings ring (nvaccess#16153)

Summary of the issue:
_set_currentSettingValue had invalid syntax, with two symbols not being referenced correctly
The function is currently not used in NVDA core, so the bug went unnoticed

Description of user facing changes
None

Description of development approach
Use correct references for symbols.

linting and typing fixes

source/synthSettingsRing.py

@@ -1,8 +1,15 @@
+# A part of NonVisual Desktop Access (NVDA)
+# This file is covered by the GNU General Public License.
+# See the file COPYING for more details.
+# Copyright (C) 2006-2024 NV Access Limited
+
+from typing import Any
+
+from autoSettingsUtils.driverSetting import BooleanDriverSetting, NumericDriverSetting
 import baseObject
 import config
-import synthDriverHandler
 import queueHandler
-from autoSettingsUtils.driverSetting import BooleanDriverSetting, NumericDriverSetting
+import synthDriverHandler
 
 
 class SynthSetting(baseObject.AutoPropertyObject):
@@ -85,12 +92,15 @@ def _set_value(self, val):
 	def _getReportValue(self, val):
 		return _("on") if val else _("off")
 
+
 class SynthSettingsRing(baseObject.AutoPropertyObject):
 	"""
-	A synth settings ring which enables the user to change to the next and previous settings and ajust the selected one
-	It was written to facilitate the implementation of a way to change the settings resembling the window-eyes way.
+	A synth settings ring which enables the user to change to the next and previous settings,
+	as well as adjust the selected one.
 	"""
 
+	settings: list[SynthSetting] | None
+
 	def __init__(self,synth):
 		try:
 			self._current = synth.initialSettingsRingSetting
@@ -107,9 +117,9 @@ def _get_currentSettingName(self):
 	def _get_currentSettingValue(self):
 		return self.settings[self._current].reportValue
 
-	def _set_currentSettingValue(self,value):
+	def _set_currentSettingValue(self, value: Any):
 		if self._current is not None:
-			self.settings[_current].value = val
+			self.settings[self._current].value = value
 
 	def next(self):
 		""" changes to the next setting and returns its name """
@@ -145,7 +155,7 @@ def updateSupportedSettings(self,synth):
 			if self._current is not None and hasattr(self,'settings')
 			else None
 		)
-		list = []
+		list: list[SynthSetting] = []
 		for s in synth.supportedSettings:
 			if not s.availableInSettingsRing: continue
 			if prevID == s.id: #restore the last setting