chore(deps): update python docker tag to v3.15.0

tests/monitoring/minimal.compose.yaml

@@ -1,7 +1,7 @@
 # Test-only services added to examples/monitoring/minimal. None of the example's services change.
 services:
   sink:
-    image: python:3.14.8-alpine
+    image: python:3.15.0-alpine
     command: ["python3", "/sink.py"]
     volumes:
       - "${DOCS_ROOT}/tests/sink.py:/sink.py:ro"

tests/monitoring/receivers.compose.yaml

@@ -8,7 +8,7 @@ services:
       - "127.0.0.1:9093:9093"
 
   sink:
-    image: python:3.14.8-alpine
+    image: python:3.15.0-alpine
     command: ["python3", "/sink.py"]
     volumes:
       - "${DOCS_ROOT}/tests/sink.py:/sink.py:ro"

tests/reverse-proxy/Dockerfile.backend

@@ -1,4 +1,4 @@
-FROM python:3.14.8-alpine
+FROM python:3.15.0-alpine
 COPY backend.py /backend.py
 EXPOSE 7681
 CMD ["python3", "-u", "/backend.py"]

tests/reverse-proxy/client.compose.yaml

@@ -2,7 +2,7 @@
 # can require that exact address in X-Forwarded-For and in the app's log.
 services:
   client:
-    image: python:3.14.8-alpine
+    image: python:3.15.0-alpine
     command: ["sleep", "infinity"]
     environment:
       AUTH_PASSWORD: "${AUTH_PASSWORD:-}"