Update python:3.14-bookworm Docker digest to 21d806f

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

tests/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.19
-FROM python:3.14-bookworm@sha256:0cc5dcf9a7aedac55ba65c69020c6953d1d3dc239600e099b86231f08e94e418
+FROM python:3.14-bookworm@sha256:21d806f67b27035aea1f6c336839e11944d6a86cdfa200e50f16de7f98bc12de
 
 RUN apt-get update \
 	&& apt-get install -y curl git apache2-utils \