Add a comment for XML requirements

Author: Mike-Dai

requirements/pip.txt

@@ -22,11 +22,15 @@ jsonfield==2.0.2
 requests==2.21.0
 requests-toolbelt==0.9.1
 slumber==0.7.1
-lxml==4.3.1
-defusedxml==0.5.0
 pyyaml==3.13
 Pygments==2.3.1
 
+# These has to be removed once APIv1 is removed
+# https://github.com/rtfd/readthedocs.org/pull/5293
+# https://github.com/rtfd/readthedocs.org/pull/3082
+lxml==4.3.1
+defusedxml==0.5.0
+
 # Basic tools
 # Redis 3.x has an incompatible change and fails
 # https://stackoverflow.com/questions/53331405/django-compress-error-invalid-input-of-type-cachekey