MM-31064: Simplify indentation (#16565)

* MM-31064: Simplify indentation

Reduce indentation where possible.

```release-note
NONE
```

Command ran to verify:
golangci-lint run --disable-all --enable golint --max-issues-per-linter=10000 --max-same-issues=100000 ./... | grep "block ends with a return state"

https://mattermost.atlassian.net/browse/MM-31064

* incorporate review comments

* enable golint for outdent rule

* fix remaining issues

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/file_info.go

@@ -72,9 +72,8 @@ func FileInfoFromJson(data io.Reader) *FileInfo {
 	var fi FileInfo
 	if err := decoder.Decode(&fi); err != nil {
 		return nil
-	} else {
-		return &fi
 	}
+	return &fi
 }
 
 func FileInfosToJson(infos []*FileInfo) string {
@@ -88,9 +87,8 @@ func FileInfosFromJson(data io.Reader) []*FileInfo {
 	var infos []*FileInfo
 	if err := decoder.Decode(&infos); err != nil {
 		return nil
-	} else {
-		return infos
 	}
+	return infos
 }
 
 func (fi *FileInfo) PreSave() {
@@ -196,13 +194,13 @@ func GetInfoForBytes(name string, data io.ReadSeeker, size int) (*FileInfo, *App
 			if info.MimeType == "image/gif" {
 				// Just show the gif itself instead of a preview image for animated gifs
 				data.Seek(0, io.SeekStart)
-				if gifConfig, err := gif.DecodeAll(data); err != nil {
+				gifConfig, err := gif.DecodeAll(data)
+				if err != nil {
 					// Still return the rest of the info even though it doesn't appear to be an actual gif
 					info.HasPreviewImage = true
 					return info, NewAppError("GetInfoForBytes", "model.file_info.get.gif.app_error", nil, err.Error(), http.StatusBadRequest)
-				} else {
-					info.HasPreviewImage = len(gifConfig.Image) == 1
 				}
+				info.HasPreviewImage = len(gifConfig.Image) == 1
 			} else {
 				info.HasPreviewImage = true
 			}