Drop attempts at py<3.6 compatibility

Wake up, it's 2023 now. Also f-strings has been used prominently already

src/Content/ContentManager.py

@@ -928,10 +928,7 @@ class ContentManager(object):
                     new_content = file
                 else:
                     try:
-                        if sys.version_info.major == 3 and sys.version_info.minor < 6:
+                        new_content = json.load(file)
-                            new_content = json.loads(file.read().decode("utf8"))
-                        else:
-                            new_content = json.load(file)
                     except Exception as err:
                         raise VerifyError(f"Invalid json file: {err}")
                 if inner_path in self.contents:

src/Db/Db.py

@@ -377,10 +377,7 @@ class Db(object):
                 if file_path.endswith("json.gz"):
                     file = helper.limitedGzipFile(fileobj=file)
 
-                if sys.version_info.major == 3 and sys.version_info.minor < 6:
+                data = json.load(file)
-                    data = json.loads(file.read().decode("utf8"))
-                else:
-                    data = json.load(file)
         except Exception as err:
             self.log.debug("Json file %s load error: %s" % (file_path, err))
             data = {}