[webapi] Add 1 TC for missing test point and delete unused files in tct-...

Impacted Suites: tct-fileapi-w3c-tests
Impacted TCs num: New 1, Update 0, Delete 3
Unit test platform: IVI
IVI test result summary: Pass 1, Fail 0, Blocked 0

Remove TC check point repeat:
new-Blob.html >>
 Blob-constructor.html

Remove files check point is not about fileapi:
URL_exists.html
BlobBuilder.html