Update to Psalm 6.x

Update performed with `composer update vimeo/psalm -w -m` to make the minimal
number of changes necessary in composer.json.

.github/workflows/continuous-integration.yml

@@ -29,10 +29,6 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - uses: actions/checkout@v4
-      # temporarily remove Psalm until ready for PHP 8.4
-      - name: remove psalm
-        if: matrix.php-versions == '8.4'
-        run: composer remove --dev --no-install vimeo/psalm psalm/plugin-phpunit
       - uses: ramsey/composer-install@v3
       - name: Run PHPUnit on Windows
         if: matrix.operating-system == 'windows-latest'
@@ -66,10 +62,6 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - uses: actions/checkout@v4
-      # temporarily remove Psalm until ready for PHP 8.4
-      - name: remove psalm
-        if: matrix.php-versions == '8.4'
-        run: composer remove --dev --no-install vimeo/psalm psalm/plugin-phpunit
       - uses: ramsey/composer-install@v3
       - name: Run Behat on Windows
         if: matrix.operating-system == 'windows-latest'

composer.json

@@ -43,7 +43,7 @@
         "doctrine/coding-standard": "^12.0",
         "phpunit/phpunit": "^10.5.39",
         "psalm/plugin-phpunit": "^0.19.1",
-        "vimeo/psalm": "^5.26.1"
+        "vimeo/psalm": "^6.0.0"
     },
     "replace": {
         "symfony/polyfill-php81": "*",
@@ -58,7 +58,7 @@
             "dealerdirect/phpcodesniffer-composer-installer": true
         },
         "platform": {
-            "php": "8.1.0"
+            "php": "8.1.99"
         }
     }
 }