Remove the old tsproto generated files. (#6083)

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### Description of the change

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Just a follow-up to #6044 which removes the now unused code.

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- ref #6013 

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Signed-off-by: Michael Nelson <minelson@vmware.com>

cmd/kubeapps-apis/buf.gen.yaml

@@ -41,16 +41,6 @@ plugins:
       - allow_merge=true
       - merge_file_name=kubeapps-apis
       - allow_repeated_fields_in_body=true
-  # ts_proto plugin generates the typescript grpc-web compliant client for each operation
-  # See https://github.com/stephenh/ts-proto
-  - name: ts_proto
-    path: ../../dashboard/node_modules/.bin/protoc-gen-ts_proto
-    out: ../../dashboard/src/gen
-    strategy: all
-    opt:
-      - outputClientImpl=grpc-web # client implementation it generates
-      - esModuleInterop=true # use imports as required in modern ts setups
-      - useOptionals=messages # use optional TypeScript properties instead of undefined
   - name: es
     opt:
       - target=ts