restore old behaviour of FindPulseAudio

Summary:
Commit ee5b036c1df4776a258c0d8067fd2eaf18875829 added a new FindPulseAudio module with a slightly different syntax than the old one. Since the old module was removed with commit 7574022825804db2274bba992d6fc4a4817c1536 plasma-desktop and plasma-pa are broken. Just adding the old syntax as synonym for fixing this.

See also https://bugs.kde.org/show_bug.cgi?id=386659

Test Plan: compile tested with plasma-desktop

Reviewers: Frameworks, cgiboudeaux

Reviewed By: cgiboudeaux

Subscribers: jriddell, ngraham, rikmills, cgiboudeaux, Build System

Tags: Frameworks, Build System

Differential Revision: https://phabricator.kde.org/D8777