Remove worker heartbeat buf exception, add process to README (#636)

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<!-- Describe what has changed in this PR -->
**What changed?**
Remove the exception added in #633, add to README explaining this
breaking change process


<!-- Tell your future self why have you made these changes -->
**Why?**
keep things working


<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**


<!-- If this breaks the Server, please provide the Server PR to merge
right after this PR was merged. -->
**Server PR**

Author: yuandrew

README.md

@@ -10,6 +10,14 @@ Install as git submodule to the project.
 
 Make your change to the temporal/proto files, and run `make` to update the openapi definitions.
 
+## Breaking changes
+
+Sometimes during initial feature development, there will be breaking API changes made. Running `make` will
+catch these changes and fail CI. If the breaking change is for a feature not yet released, a temporary `ignore`
+line can be added to `buf.yaml` to pass CI. This is
+[an example](https://github.com/temporalio/api/pull/608/files#diff-1a5ba9cba93e971f532139f694d7da802776bfe578e3f753b9c3f25968dbf42dL16)
+of adding such an exception. A subsequent PR will be needed to then disable to exception once it's been merged in.
+
 ## License
 
 MIT License, please see [LICENSE](LICENSE) for details.

buf.yaml

@@ -13,9 +13,6 @@ breaking:
     - WIRE_JSON
   ignore:
     - google
-    # TODO (yuandrew): remove this. Added for "heartbeat" changes
-    - temporal/api/workflowservice/v1/request_response.proto
-    - temporal/api/worker/v1/message.proto
 lint:
   use:
     - DEFAULT