Remove unnecessary spying in MockingOomAdjusterTests

ProcessRecord and WindowProcessController have a circular reference to
each other, so spying on a ProcessRecord will cause the reference cycle
to break. Removed some unnessary spy usage in MockingOomAdjuster to fix
this reference breakage for the pushActivityToOomAdjuster flagged code,
which relies on WPC reference to ProcessRecord.

Flag: EXEMPTED test fix
Bug: 401350380
Test: atest MockingOomAdjusterTests
Change-Id: If1805d581f4b7f31fbd584a17928146b200baf2c