bug #30937 [Profiler] Fix graph text color (dFayet)

This PR was merged into the 4.3-dev branch.

Discussion
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[Profiler] Fix graph text color

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | -   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | -

#30450 introduces bad text color for graph items in the profiler, specially in dark theme mode.

### before/after

![Capture d’écran de 2019-04-06 21-38-29](https://user-images.githubusercontent.com/7721219/55674505-ff79ad80-58b5-11e9-9a29-8359ff07673d.png)

![Capture d’écran de 2019-04-06 21-42-26](https://user-images.githubusercontent.com/7721219/55674507-030d3480-58b6-11e9-8dee-395e2046e7ca.png)

There is a small change for default theme

### before/after

![Capture d’écran de 2019-04-06 21-51-46](https://user-images.githubusercontent.com/7721219/55674538-4ff10b00-58b6-11e9-8aed-2621bdde673d.png)

![Capture d’écran de 2019-04-06 21-52-15](https://user-images.githubusercontent.com/7721219/55674540-52ebfb80-58b6-11e9-9d94-68743187aba2.png)

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Commits
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44d9fbe995 Fix graph text color

src/Symfony/Bundle/WebProfilerBundle/Resources/views/Collector/time.css.twig

@@ -53,7 +53,7 @@
     font-size: 12px;
     line-height: 12px;
     font-weight: normal;
-    color: var(--color-text);
+    fill: var(--color-text);
 }
 
 .timeline-graph .timeline-label .timeline-sublabel {