fix: Fix multiline expression (#4297)

## Description

1. What is this PR about (link the issue and add a short description)

## Steps for reproduction

1. click button
2. expect xyz

## Code Review

- [ ] hi @kof, I need you to do
  - conceptual review (architecture, feature-correctness)
  - detailed review (read every line)
  - test it on preview

## Before requesting a review

- [ ] made a self-review
- [ ] added inline comments where things may be not obvious (the "why",
not "what")

## Before merging

- [ ] tested locally and on preview environment (preview dev login:
5de6)
- [ ] updated [test
cases](https://github.com/webstudio-is/webstudio/blob/main/apps/builder/docs/test-cases.md)
document
- [ ] added tests
- [ ] if any new env variables are added, added them to `.env` file

Author: istarkov

apps/builder/app/builder/shared/expression-editor.tsx

@@ -268,8 +268,6 @@ const variableMatcher = new MatchDecorator({
   regexp: /(\$ws\$dataSource\$\w+)/g,
 
   decorate: (add, from, _to, match, view) => {
-    const startPos = match.index;
-
     const name = match[1];
     const [{ aliases }] = view.state.facet(VariablesData);
 
@@ -282,7 +280,8 @@ const variableMatcher = new MatchDecorator({
     if (dataSourceId === undefined) {
       return;
     }
-    const endPos = startPos + dataSourceId.length;
+
+    const endPos = from + dataSourceId.length;
 
     add(
       from,