Set default dda version in BYOC Dockerfile (#42291)

### What does this PR do?
Sets default DDA version in BYOC Dockerfile to v0.29.0

### Motivation
As a follow up to #41548, this PR sets a default DDA_VERSION in the BYOC Dockerfile which was needed to run BYOC locally.

### Describe how you validated your changes

### Additional Notes


Co-authored-by: stanley.liu <stanley.liu@datadoghq.com>

Author: liustanley

Dockerfiles/agent-ddot/Dockerfile.agent-otel

@@ -9,7 +9,7 @@ FROM ubuntu:${UBUNTU_VERSION} AS builder
 ARG AGENT_REPO
 ARG AGENT_VERSION
 ARG AGENT_BRANCH
-ARG DDA_VERSION
+ARG DDA_VERSION=v0.29.0
 ENV DEBIAN_FRONTEND=noninteractive
 
 # Set the working directory