minor #9232 Fixed the path of an image (javiereguiluz)

This PR was merged into the 2.8 branch.

Discussion
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Fixed the path of an image

Sorry for all these pull requests about this SVG image. Hopefully this will be the last one. We've made some changes on the symfony.com server too to prepare for images like this that are embedded using `<object>` instead of `<img>`. We'll see if it works.

Commits
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15344d9 Fixed the path of an image

Author: javiereguiluz

security/guard_authentication.rst

@@ -434,7 +434,7 @@ The picture below shows how Symfony calls Guard Authenticator methods:
 
 .. raw:: html
 
-    <object data="./_images/security/authentication-guard-methods.svg" type="image/svg+xml"></object>
+    <object data="../_images/security/authentication-guard-methods.svg" type="image/svg+xml"></object>
 
 .. _guard-customize-error: