minor #15285 Update docs-builder to version 0.15 (Nyholm)

This PR was squashed before being merged into the 4.4 branch.

Discussion
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Update docs-builder to version 0.15

We had a lot of errors when building the docs related to php-attributres. They are resolved now.

I don't get any errors when I build locally on 4.4 and 5.x. So I (naively) assume everything is fine.

I don't know why we have not updated before, If there is a problem I don't know about please share.

Commits
-------

3837eba Update docs-builder to version 0.15

Author: javiereguiluz

.github/workflows/ci.yaml

@@ -49,7 +49,7 @@ jobs:
             -   name: "Set-up PHP"
                 uses: shivammathur/setup-php@v2
                 with:
-                    php-version: 7.2
+                    php-version: 8.0
                     coverage: none
                     tools: "composer:v2"
 

_build/composer.json

@@ -6,17 +6,17 @@
     ],
     "config": {
         "platform": {
-            "php": "7.2.9"
+            "php": "7.4.14"
         },
         "preferred-install": {
             "*": "dist"
         },
         "sort-packages": true
     },
     "require": {
-        "php": ">=7.2.9",
-        "symfony/console": "^4.4",
-        "symfony/docs-builder": "^0.12.0",
-        "symfony/process": "^4.4"
+        "php": ">=7.4",
+        "symfony/console": "^5.2",
+        "symfony/docs-builder": "^0.15.0",
+        "symfony/process": "^5.2"
     }
 }