MPEG4Writer: Remove timestamp validation

Timestamp validation method that was added doesn't work as expected
when system time is sent as timestamp to the MPEG4Writer.

Bug: 331723380
Test: atest CtsMediaMuxerTestCases
Test: atest CtsMediaV2TestCases:MuxerTest
Test: atest CtsMediaV2TestCases:MuxerUnitTest

Change-Id: I9cf28cae0c4836035290123ae33cf6d94052585e
2 files changed