Add external/python/dateutil to the manifest.

Bug: 80423803
Test: None
Change-Id: I53dcf877d1737134849dd2c2b8ba6b85829588a7

default.xml

@@ -289,6 +289,7 @@
   <project path="external/python/cachetools" name="platform/external/python/cachetools" groups="vts,pdk" />
   <project path="external/python/cpython2" name="platform/external/python/cpython2" groups="pdk" />
   <project path="external/python/cpython3" name="platform/external/python/cpython3" groups="pdk" />
+  <project path="external/python/dateutil" name="platform/external/python/dateutil" groups="pdk" />
   <project path="external/python/dill" name="platform/external/python/dill" groups="vts,pdk" />
   <project path="external/python/enum" name="platform/external/python/enum" groups="vts,pdk" />
   <project path="external/python/enum34" name="platform/external/python/enum34" groups="vts,pdk" />