Mark many attributes as read-only properties (#7591)

stubs/html5lib/html5lib/_inputstream.pyi

@@ -82,7 +82,8 @@ class EncodingBytes(bytes):
     def getPosition(self): ...
     position: Any
     def getCurrentByte(self): ...
-    currentByte: Any
+    @property
+    def currentByte(self): ...
     def skip(self, chars=...): ...
     def skipUntil(self, chars): ...
     def matchBytes(self, bytes): ...

stubs/html5lib/html5lib/treebuilders/etree_lxml.pyi

@@ -15,7 +15,8 @@ class DocumentType:
 class Document:
     def __init__(self) -> None: ...
     def appendChild(self, element) -> None: ...
-    childNodes: Any
+    @property
+    def childNodes(self): ...
 
 def testSerializer(element): ...
 def tostring(element): ...