linux-pulseaudio: Fix bad channels message format

[dimtpap]

Description

Fix the format specifiers in the message string for unsupported audio channels in the linux-pulseaudio plugin.

Motivation and Context

I was debugging an issue and the message in the log was not helpful.

How Has This Been Tested?

Add a PulseAudio output capture and target a sink with unsupported channels.
Before:

info: pulse-input: 	 channels not supported by OBS,using  instead for recording

After:

info: pulse-input: 9 channels not supported by OBS, using 2 instead for recording

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[tytan652]

LGTM