Fix CI pipeline warnings (#446)

- gofumpt: Remove deprecated flag
- golangci-lint: Disable deprecated linters; add reason in config

Author: Shashank Sinha

.golangci.yml

@@ -31,6 +31,10 @@ linters:
       - wsl
       - exhaustivestruct
       - varnamelen
+      - maligned          //deprecated
+      - scopelint         //deprecated
+      - golint            //deprecated
+      - interfacer        //deprecated
 issues:
   exclude-use-default: false
   exclude:

Makefile

@@ -83,7 +83,7 @@ FILES = $(shell find . -type f -name '*.go' -not -path "./vendor/*")
 
 format:                     ## Format source code.
 	go mod tidy
-	bin/gofumpt -l -w -s $(FILES)
+	bin/gofumpt -l -w $(FILES)
 	bin/goimports -local github.com/percona/mongodb_exporter -l -w $(FILES)
 
 check:                      ## Run checks/linters