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>

app/plugin_api.go

@@ -50,16 +50,16 @@ func (api *PluginAPI) LoadPluginConfiguration(dest interface{}) error {
 		finalConfig[strings.ToLower(setting)] = value
 	}
 
-	if pluginSettingsJsonBytes, err := json.Marshal(finalConfig); err != nil {
+	pluginSettingsJsonBytes, err := json.Marshal(finalConfig)
+	if err != nil {
 		api.logger.Error("Error marshaling config for plugin", mlog.Err(err))
 		return nil
-	} else {
-		err := json.Unmarshal(pluginSettingsJsonBytes, dest)
-		if err != nil {
-			api.logger.Error("Error unmarshaling config for plugin", mlog.Err(err))
-		}
-		return nil
 	}
+	err = json.Unmarshal(pluginSettingsJsonBytes, dest)
+	if err != nil {
+		api.logger.Error("Error unmarshaling config for plugin", mlog.Err(err))
+	}
+	return nil
 }
 
 func (api *PluginAPI) RegisterCommand(command *model.Command) error {