[Docs] Speed up build environment set-up (#34240)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

.readthedocs.yaml

@@ -9,13 +9,14 @@ build:
     python: "3.12"
   jobs:
     post_checkout:
-      - git fetch --unshallow || true
+      - git fetch origin main --unshallow --no-tags --filter=blob:none || true
+    pre_create_environment:
+      - pip install uv
+    create_environment:
+      - uv venv $READTHEDOCS_VIRTUALENV_PATH
+    install:
+      - uv pip install --python $READTHEDOCS_VIRTUALENV_PATH/bin/python --no-cache-dir -r requirements/docs.txt 
 
 mkdocs:
   configuration: mkdocs.yaml
   fail_on_warning: true
-
-# Optionally declare the Python requirements required to build your docs
-python:
-  install:
-    - requirements: requirements/docs.txt