Use actual UCXX versioning (#215)

Further details [here](rapidsai/docs#503 (comment)).

Authors:
  - Jake Awe (https://github.com/AyodeAwe)

Approvers:
  - Ray Douglass (https://github.com/raydouglass)

URL: #215

ci/build_docs.sh

@@ -27,7 +27,7 @@ rapids-mamba-retry install \
 
 export UCXX_VERSION="$(sed -E -e 's/^([0-9]+)\.([0-9]+)\.([0-9]+).*$/\1.\2.\3/' VERSION)"
 export UCXX_VERSION_MAJOR_MINOR="$(sed -E -e 's/^([0-9]+)\.([0-9]+)\.([0-9]+).*$/\1.\2/' VERSION)"
-export RAPIDS_VERSION_NUMBER="24.06"
+export RAPIDS_VERSION_NUMBER="$UCXX_VERSION_MAJOR_MINOR"
 export RAPIDS_DOCS_DIR="$(mktemp -d)"
 
 rapids-logger "Build CPP docs"