fix(docs): Updated .readthedocs.yml

Minor typing error fix in .readthedocs.yml file.

Closes https://github.com/espressif/esp-idf/pull/13191

.readthedocs.yml

@@ -15,7 +15,7 @@ python:
   install:
     - requirements: docs/requirements.txt
 
-# We need to list all the submodules included in documenation build by DOxygen
+# We need to list all the submodules included in documenation build by Doxygen
 submodules:
   include:
     - components/mqtt/esp-mqtt