message: Update pugixml to reference upstream master
diff: @@ -8,7 +8,7 @@ readonly name="pugixml"
  readonly ownership="pugixml Upstream <robot@adios2>"
  readonly subtree="thirdparty/pugixml/pugixml"
  readonly repo="https://github.com/zeux/pugixml.git"
  -readonly tag="v1.8.1"
  +readonly tag="master"
  readonly shortlog="true"
  readonly paths="
  src/pugiconfig.hpp
  