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>

store/sqlstore/plugin_store.go

@@ -120,9 +120,8 @@ func (ps SqlPluginStore) CompareAndSet(kv *model.PluginKeyValue, oldValue []byte
 			// need to return it.
 			if IsUniqueConstraintError(err, []string{"PRIMARY", "PluginId", "Key", "PKey", "pkey"}) {
 				return false, nil
-			} else {
-				return false, errors.Wrap(err, "failed to insert PluginKeyValue")
 			}
+			return false, errors.Wrap(err, "failed to insert PluginKeyValue")
 		}
 	} else {
 		currentTime := model.GetMillis()