minor #15080 Update EngineInterface.php (johnnypeck)

This PR was submitted for the 2.8 branch but it was merged into the 2.3 branch instead (closes #15080).

Discussion
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Update EngineInterface.php

Grammer in doc comment.

Commits
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d60b2bb Update EngineInterface.php

src/Symfony/Component/Templating/EngineInterface.php

@@ -14,7 +14,7 @@ namespace Symfony\Component\Templating;
 /**
  * EngineInterface is the interface each engine must implement.
  *
- * All methods relies on a template name. A template name is a
+ * All methods rely on a template name. A template name is a
  * "logical" name for the template, and as such it does not refer to
  * a path on the filesystem (in fact, the template can be stored
  * anywhere, like in a database).