Fix OEMCrypto Tests

(This is a merge of http://go/wvgerrit/14810)

By making this constant unsigned, all calculations in EXPECT_ALMOST
were cast to unsigned, leading to underflow problems when it was
subtracted from zero.

Change-Id: Iefc4e30604c45fec8b203375074b26fb12ec385f

libwvdrmengine/oemcrypto/test/oemcrypto_test.cpp

@@ -59,7 +59,7 @@ const int kShortSleep = 1 * kSpeedMultiplier;
 const int kLongSleep = 2 * kSpeedMultiplier;
 const uint32_t kDuration = 2 * kSpeedMultiplier;
 const uint32_t kLongDuration = 5 * kSpeedMultiplier;
-const uint32_t kAlmostRange = 3 * kSpeedMultiplier;
+const int32_t kAlmostRange = 3 * kSpeedMultiplier;
 }  // namespace
 
 namespace wvoec {