Bump flatted from 3.3.3 to 3.4.2 in /webapp (#985)

* Bump flatted from 3.3.3 to 3.4.2 in /webapp

Bumps [flatted](https://github.com/WebReflection/flatted) from 3.3.3 to 3.4.2.
- [Commits](WebReflection/flatted@v3.3.3...v3.4.2)

---
updated-dependencies:
- dependency-name: flatted
  dependency-version: 3.4.2
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

* Fixing linter issue with govet reading webapp

* Fixing year for license files

* Excluding path for golangci

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: avasconcelos114 <andre.onogoro@gmail.com>

Author: dependabot[bot]

.golangci.yml

@@ -38,6 +38,8 @@ linters:
     unqueryvet:
       check-sql-builders: true
   exclusions:
+    paths:
+      - webapp/node_modules
     rules:
       - path: server/configuration.go
         linters:

Makefile

@@ -203,9 +203,9 @@ endif
 # weird reports at golangci-lint step
 ifneq ($(HAS_SERVER),)
 	@echo Running golangci-lint
-	$(GO) vet ./...
+	$(GO) vet $$($(GO) list ./... | grep -v /webapp/)
 	$(GOBIN)/golangci-lint run ./...
-	$(GO) vet -vettool=$(GOBIN)/mattermost-govet -license -license.year=2018 ./...
+	$(GO) vet -vettool=$(GOBIN)/mattermost-govet -license -license.year=2018 $$($(GO) list ./... | grep -v /webapp/)
 endif
 
 ## Builds the server, if it exists, for all supported architectures, unless MM_SERVICESETTINGS_ENABLEDEVELOPER is set