minor #18393 [VarDumper] Relax tests to pass on appveyor (nicolas-grekas)

This PR was merged into the 2.8 branch.

Discussion
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[VarDumper] Relax tests to pass on appveyor

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

6dbb117 [VarDumper] Relax tests to pass on appveyor

src/Symfony/Component/VarDumper/Tests/Caster/SplCasterTest.php

@@ -55,12 +55,6 @@ SplFileInfo {
   pathname: "https://google.com/about"
   extension: ""
   realPath: false
-  writable: false
-  readable: false
-  executable: false
-  file: false
-  dir: false
-  link: false
 %A}
 EOTXT
             ),