Update AccessibilityService global headset action docs to fully recognize calling behavior

There's already a CTS test(http://shortn/_w3OkkmZCO5) to make sure the global action affects calls.

This establishes in javadocs that this action should affect calling states for accessibility users.

Bug: 301451932
Test: n/a docs
Change-Id: Iba81f093320d112515f4e3f55dc049704326bb10
1 file changed