bug symfony#16970 [HttpKernel] HttpCache: remove an ESI instance checking (voronkovich)

This PR was merged into the 3.0 branch.

Discussion
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[HttpKernel] HttpCache: remove an ESI instance checking

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

This checking was added by this commit symfony@32d964b, but now it's not needed

Commits
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7528134 Removed ESI instance check

Author: Tobion

src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php

@@ -153,16 +153,10 @@ public function getKernel()
     /**
      * Gets the Surrogate instance.
      *
-     * @throws \LogicException
-     *
      * @return SurrogateInterface A Surrogate instance
      */
     public function getSurrogate()
     {
-        if (!$this->surrogate instanceof Esi) {
-            throw new \LogicException('This instance of HttpCache was not set up to use ESI as surrogate handler. You must overwrite and use createSurrogate');
-        }
-
         return $this->surrogate;
     }