minor symfony#24655 [4.0][HttpKernel] Remove composer require-dev "symfony/class-loader" (siwinski)

This PR was merged into the 4.0-dev branch.

Discussion
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[4.0][HttpKernel] Remove composer require-dev "symfony/class-loader"

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

ClassLoader component is removed in version 4.  This pull request removes HttpKernel's `composer.json` 's `require-dev` of the `symfony/class-loader` package.

Commits
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f358533 [HttpKernel] Remove composer require-dev "symfony/class-loader"

Author: fabpot

src/Symfony/Component/HttpKernel/composer.json

@@ -24,7 +24,6 @@
     },
     "require-dev": {
         "symfony/browser-kit": "~3.4|~4.0",
-        "symfony/class-loader": "~3.4|~4.0",
         "symfony/config": "~3.4|~4.0",
         "symfony/console": "~3.4|~4.0",
         "symfony/css-selector": "~3.4|~4.0",