Update symfony/var-dumper requirement from ^4.0 to ^5.0

[dependabot-preview]

Updates the requirements on symfony/var-dumper to permit the latest version.

Changelog

Sourced from symfony/var-dumper's changelog.

CHANGELOG

4.4.0

• added VarDumperTestTrait::setUpVarDumper() and VarDumperTestTrait::tearDownVarDumper()
  to configure casters & flags to use in tests
• added ImagineCaster and infrastructure to dump images
• added the stamps of a message after it is dispatched in TraceableMessageBus and MessengerDataCollector collected data
• added UuidCaster
• made all casters final
• added support for the NO_COLOR env var (https://no-color.org/)

4.3.0

• added DsCaster to support dumping the contents of data structures from the Ds extension

4.2.0

• support selecting the format to use by setting the environment variable VAR_DUMPER_FORMAT to html or cli

4.1.0

• added a ServerDumper to send serialized Data clones to a server
• added a ServerDumpCommand and DumpServer to run a server collecting
  and displaying dumps on a single place with multiple formats support
• added CliDescriptor and HtmlDescriptor descriptors for server:dump CLI and HTML formats support

4.0.0

• support for passing \ReflectionClass instances to the Caster::castObject()
  method has been dropped, pass class names as strings instead
• the Data::getRawData() method has been removed
• the VarDumperTestTrait::assertDumpEquals() method expects a 3rd $filter = 0
  argument and moves $message = '' argument at 4th position.
• the VarDumperTestTrait::assertDumpMatchesFormat() method expects a 3rd $filter = 0
  argument and moves $message = '' argument at 4th position.

3.4.0

• added AbstractCloner::setMinDepth() function to ensure minimum tree depth
• deprecated MongoCaster

2.7.0

... (truncated)

Commits

• 956b8b6 Allow PHP ^7.2.5
• 98c8189 Merge branch '4.4'
• eade289 Allow \Throwable $previous everywhere
• f507d24 Merge branch '4.4'
• c85ac54 Add support for NO_COLOR env var
• dca3a24 [VarDumper] Clean casters @​final annotations
• 0429722 Merge branch '4.4'
• fb5bf9e [VarDumper] Mark StubCaster as @​final
• cb7bd8f Merge branch '4.4'
• d36dd76 [VarDumper] fix tests & displaying generators
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #57.