Update sourcefile field setting IsFilterable to true.

[jaliyaudagedara]

Purpose

In here,

var filter = (fileName is null) ? null : $"sourcefile eq '{Path.GetFileName(fileName)}'";

for this to work, sourcefile should be filterable.

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe: