Revert "Make phan ignore JsonSerializable redefinition"
Revert "Make phan ignore JsonSerializable redefinition"

This reverts commit 13956265c1d607565d0583b77e7e80b1cc287efb.

The Wikimedia CI jobs running phan were installing mediawiki development
dependencies which might overlap with the dependencies from the
extension. Ultimately phan failed with:

includes/RemoteSchema.php:9
PhanRedefinedInheritedInterface
\RemoteSchema inherits abstract Interface \JsonSerializable declared at
internal:0 which is also declared at
../../vendor/jakub-onderka/php-parallel-lint/src/JsonSerializable.php:4.
This may lead to confusing errors.

If7171a6d46473b0bb05e3adaeb40229e7881c2b6 adjusts the CI configuration
to no more install MediaWiki core development dependencies and solely
relies on mediawiki/vendor.git. That prevents the duplicate interface
definition.

Bug: T223397
Depends-On: If7171a6d46473b0bb05e3adaeb40229e7881c2b6
Change-Id: I794fbffe59104f138802bc6ded1a9d9a58ba9437

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo