Fix CodeSniffer errors and warnings

The issue summary should always describe what the issue is trying to fix and, in the case, of coding standards issues, show which command has been used, which arguments have been used, and which report that command shown.

Mohd Sahzad → made their first commit to this issue’s fork.

Working on it.

The 8.x-1.x branch is no longer supported; any change needs to be done in the 2.x branch.

avpaderno → changed the visibility of the branch 3034265-fix-the-errorswarnings to hidden.

The changes are just for using the short syntax for array and adding a @var line for a property declaration.

IMO, they are so small that they should be fixed when fixing other issues in the code, if those issues are present. Otherwise, the merge request in this issue can be merged, at project maintainers' discretion.

The changes looks good to me
Moving it to RTBC.