Update symfony/filesystem requirement from 8.0.* to 8.1.*

[dependabot]

Updates the requirements on symfony/filesystem to permit the latest version.

Release notes

Sourced from symfony/filesystem's releases.

v8.1.0

Changelog (symfony/filesystem@v8.1.0-BETA2...v8.1.0)

• no significant changes

Changelog

Sourced from symfony/filesystem's changelog.

CHANGELOG

8.1

• Deprecate calling Filesystem::mirror() with option copy_on_windows, use option follow_symlinks instead.

7.1

• Add the Filesystem::readFile() method

7.0

• Add argument $lock to Filesystem::appendToFile()

5.4

• Add Path class
• Add $lock argument to Filesystem::appendToFile()

5.0.0

• Filesystem::dumpFile() and appendToFile() don't accept arrays anymore

4.4.0

• support for passing a null value to Filesystem::isAbsolutePath() is deprecated and will be removed in 5.0
• tempnam() now accepts a third argument $suffix.

4.3.0

• support for passing arrays to Filesystem::dumpFile() is deprecated and will be removed in 5.0
• support for passing arrays to Filesystem::appendToFile() is deprecated and will be removed in 5.0

4.0.0

• removed LockHandler
• Support for passing relative paths to Filesystem::makePathRelative() has been removed.

3.4.0

... (truncated)

Commits

• 99aec13 Add call to backers in README files
• 1cbffe0 [Filesystem] Various fixes and hardenings
• 1f9966f Merge branch '8.0' into 8.1
• 224db91 Merge branch '7.4' into 8.0
• d721ea6 Merge branch '6.4' into 7.4
• c507b07 [Filesystem] preserve source mode when copying files
• 5f0d8cd Merge branch '8.0' into 8.1
• d1ec454 Merge branch '7.4' into 8.0
• dcd8f96 Update XSD references in phpunit.xml.dist files
• f8f83a3 Merge branch '7.4' into 8.0
• Additional commits viewable in compare view

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[wtorsi]

Superseded by the Symfony 8.1 release-line migration: main now pins this requirement at 8.1.* (merged via the 8.1 release PR).

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version. You can also ignore all major, minor, or patch releases for a dependency by adding an ignore condition with the desired update_types to your config file.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.