fix(otel): silence otelsdk warnings in build-one

The build-env images set an OTEL traces/logs/metrics exporter, but otelsdk
isn't installed, so pak's otel instrumentation logs 'no package called otelsdk'.
OTEL_SDK_DISABLED is ignored by the R otel package; it gates on
OTEL_R_<SIGNAL>_EXPORTER. Set those to 'none' so the R otel providers are a
clean no-op (without disabling OTel for any non-R tooling).

docker/build-one.Dockerfile

@@ -30,6 +30,9 @@ RUN --mount=type=secret,id=b2_access,required=true \
     export GITHUB_PAT="$(cat /run/secrets/github_pat 2>/dev/null || true)" && \
     export GIT_TERMINAL_PROMPT=0 && \
     export OTEL_SDK_DISABLED=true && \
+    export OTEL_R_TRACES_EXPORTER=none && \
+    export OTEL_R_LOGS_EXPORTER=none && \
+    export OTEL_R_METRICS_EXPORTER=none && \
     XVFB=$(command -v xwfb-run 2>/dev/null || command -v xvfb-run || true); \
     XVFB_ARGS=""; \
     if command -v xwfb-run >/dev/null 2>&1; then dnf install -y -q weston 2>/dev/null; XVFB_ARGS="-c weston"; fi; \