Refactor share api tests

[amrita-shrestha]

Description

Currently, we don't have an API step where sharer removes sharee
The previous steps are

 * @When /^user "([^"]*)" (?:deletes|unshares) (?:file|folder) "([^"]*)" using the WebDAV API$
 * @Given /^user "([^"]*)" has (deleted|unshared) (file|folder) "([^"]*)"$/
 * @Given /^user "([^"]*)" has (deleted|unshared) the following (files|folders|resources)$/

Look over the whole share-related tests-suite and find out the scenario where we delete shared resources in place of unshare resources. Refactor those scenarios.

Done

• step, where sharer removes sharee, has been added in this PR [full-ci][tests-only]Extend notification api tests #6324

[SwikritiT]

@S-Panta will be working on this

[saw-jan]

Done in #6608