git_submodules: Change the upstream repo urls for the git submodules

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "components/homekit/json_parser/upstream"]
 	path = components/homekit/json_parser/upstream
-	url = https://github.com/shahpiyushv/json_parser.git
+	url = https://github.com/espressif/json_parser.git
 [submodule "components/homekit/json_generator/upstream"]
 	path = components/homekit/json_generator/upstream
-	url = https://github.com/shahpiyushv/json_generator.git
+	url = https://github.com/espressif/json_generator.git

README.md

@@ -33,6 +33,8 @@ git clone --recursive https://github.com/espressif/esp-homekit-sdk.git
 
 > Note the --recursive option. This is required to pull in the JSON dependencies into esp-homekit-sdk. In case you have already cloned the repository without this option, execute this to pull in the submodules:
 > `git submodule update --init --recursive`
+>
+> If you had already cloned the repository and submodules earlier, you may have to execute `git submodule sync --recursive` once since the submodule paths have changed.
 
 
 ### Compile and Flash