Update buildifier warnings (bazelbuild#1866)

.bazelci/presubmit.yml

@@ -1,13 +1,8 @@
 ---
 buildifier:
   version: 4.0.1
-  # Check for issues with the format of our bazel config files.
-  # All warnings from https://github.com/bazelbuild/buildtools/blob/master/WARNINGS.md
-  # are enabled except:
-  # rule-impl-return, uninitialized, return-value, rule-impl-return
-  # TODO (suvanjan): Re-enable once issues are fixed.
-  warnings: "attr-cfg,attr-license,attr-non-empty,attr-output-default,attr-single-file,confusing-name,constant-glob,ctx-actions,ctx-args,depset-iteration,depset-union,dict-concatenation,duplicated-name,filetype,function-docstring,git-repository,http-archive,integer-division,load,load-on-top,module-docstring,name-conventions,native-build,native-package,no-effect,out-of-order-load,output-group,package-name,package-on-top,redefined-variable,repository-name,same-origin-load,string-iteration,unreachable,unsorted-dict-items,unused-variable"
-bazel: 4.0.0 # keep in sync with .bazelversion
+  warnings: "-rule-impl-return,-return-value,-function-docstring-args,-print,-skylark-comment,-provider-params,-unnamed-macro"
+bazel: 4.0.0
 tasks:
   default_workspace_ubuntu1804:
     platform: ubuntu1804