[compiler-rt][XRay] Remove unnecessary assertion.
[compiler-rt][XRay] Remove unnecessary assertion.

This assert only causes issues with signed/unsigned comparisons.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@279819 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt