Enable Tracing in Prometheus Source

[slinkydeveloper]

Problem
Enable Tracing configuration for Prometheus Source

Persona:
Event consumer/Event producer

Exit Criteria
Prometheus Source tracing works

Time Estimate (optional):
1

Additional context (optional)
In order to enable that, we just need to reflect the changes from knative/eventing#3026.

An example on how to do that is provided by these changes to apiserversource:

• https://github.com/knative/eventing/pull/3026/files#diff-d99b024fa0cd240e5a9ba150e807531a
• https://github.com/knative/eventing/pull/3026/files#diff-d86a389c49e177be3527a5acd33138ae
• https://github.com/knative/eventing/pull/3026/files#diff-edbbfc473b7a21fb3031e92071dcca86

[slinkydeveloper]

/assign