Remove coveralls token - it's not necessary when running on Travis. (#293)

Author: igorpeshansky

.coveralls.yml

@@ -15,8 +15,3 @@ script:
 - 'if [[ "${TRAVIS_PULL_REQUEST_SLUG:-Stackdriver/stackdriver-prometheus-sidecar}" == "Stackdriver/stackdriver-prometheus-sidecar" ]]; then make goveralls; fi'
 # TODO(jkohen): `make goveralls` is causing a diff in go.mod. Prevent that and uncomment the line below.
 #- git diff --exit-code
-
-# Contains tokens for Coveralls. See https://docs.coveralls.io/go
-env:
-  global:
-    secure: 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

.travis.yml

@@ -93,11 +93,8 @@ staticcheck: $(STATICCHECK)
 	$(STATICCHECK) $(pkgs)
 
 goveralls: cover $(GOVERALLS)
-ifndef COVERALLS_TOKEN
-	$(error COVERALLS_TOKEN is undefined, follow https://docs.coveralls.io/go to create one and go to https://coveralls.io to retrieve existing ones)
-endif
 	@echo ">> running goveralls"
-	$(GOVERALLS) -coverprofile=coverage.out -service=travis-ci -repotoken "${COVERALLS_TOKEN}"
+	$(GOVERALLS) -coverprofile=coverage.out -service=travis-ci
 
 build: promu
 	@echo ">> building binaries"