Makefile: rm check and lint targets

The targets being removed were used by Travis CI, which is long gone.
Golangci-lint is now run by GHA CI without any help from the Makefile.

If a developer wants to run it locally,
they probably have it installed already, and typing

	golangci-lint run ./...

is relatively easy.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Author: kolyshkin

Makefile

@@ -10,30 +10,17 @@ build: bin/go-md2man
 clean:
 	@rm -rf bin/*
 
-.PHONY: check
-check: lint
-
 .PHONY: test
 test:
 	@go test $(TEST_FLAGS) ./...
 
-.PHONY: lint
-lint:
-	@$(LINTER_BIN) run --new-from-rev "HEAD~$(git rev-list master.. --count)" ./...
-
 bin/go-md2man: actual_build_flags := $(BUILD_FLAGS) -o bin/go-md2man
 bin/go-md2man: bin
 	@CGO_ENABLED=0 go build $(actual_build_flags)
 
 bin:
 	@mkdir ./bin
 
-$(LINTER_BIN): linter_bin_path := $(shell which $(LINTER_BIN))
-$(LINTER_BIN):
-	@if [ -z $(linter_bin_path) ] || [ ! -x $(linter_bin_path) ]; then \
-		curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(shell go env GOPATH)/bin v1.15.0; \
-	fi
-
 .PHONY: mod
 mod:
 	@go mod tidy