vdk-dag: replace DAG diagrams with consistently colored ones (#2173)

What:
Replace DAG diagrams with consistently colored ones.

Why: 
To have a consistent and better-looking docs.

Signed-off-by: Yoan Salambashev <[email protected]>

Author: yonitoo

Diff for: examples/dag-example/README.md

@@ -439,8 +439,8 @@ vdk deploy -n ingest-job2 -t my-team -p ingest-job2 -r "dag-example" -u http://l
 ```
 
 ```console
-vdk create -n read-job -t my-team --no-template -u http://localhost:8092 && \
-vdk deploy -n read-job -t my-team -p read-job -r "dag-example" -u http://localhost:8092
+vdk create -n read-data-job -t my-team --no-template -u http://localhost:8092 && \
+vdk deploy -n read-data-job -t my-team -p read-data-job -r "dag-example" -u http://localhost:8092
 ```
 
 ```console

Diff for: examples/dag-example/images/dag-graph.png

@@ -51,7 +51,7 @@ When defining a job to be run following attributes are supported:
 The following example dependency graph can be implemented with below code.
 
 
-![img_2.png](img_2.png)
+![example_dag.png](example_dag.png)
 
 In this example what happens is:
 * Job 1 will execute.