chore: fix some comments

Signed-off-by: longxiangqiao <longxiangqiao@qq.com>

electrum/gui/qt/history_list.py

@@ -307,7 +307,7 @@ class HistoryModel(CustomModel, Logger):
                 # add child to parent
                 node.addChild(child_node)
 
-        # compute balance once all children have beed added
+        # compute balance once all children have been added
         balance = 0
         for node in self._root._children:
             balance += node._data['value'].value

electrum/gui/qt/rate_limiter.py

@@ -98,7 +98,7 @@ class RateLimiter(Logger):
                 self.timer.start(int(diff*1e3))
                 #self.logger.debug("deferring")
         else:
-            # We had a timer active, which means as future call will occur. So return early and let that call happenin the future.
+            # We had a timer active, which means as future call will occur. So return early and let that call happen in the future.
             # Note that a side-effect of this aborted invocation was to update self.saved_args.
             pass
             #self.logger.debug("ignoring (already scheduled)")