[OpenMP][NFC] Fix wrong debug assertion.

[AndreyChurbanov]

Summary

Normalized bounds of chunk of iterations to steal from are inclusive, so upper bound should not be decremented in expression to check.
Problem was in attempt to steal iterations 0:0, that caused assertion after wrong decrement.
Reported in comment to https://reviews.llvm.org/D103648.

[hbae]

LGTM

openmp/runtime/src/kmp_dispatch.cpp

#endif
             remaining = vold.p.ub - vold.p.count;
             // try to steal 1/4 of remaining
             // TODO: is this heuristics good enough??
             if (remaining > 7) {
               vnew.p.ub -= remaining >> 2; // steal from tail of victim's range
             } else {
               vnew.p.ub -= 1; // steal 1 chunk of 1..7 remaining
             }
-            KMP_DEBUG_ASSERT((vnew.p.ub - 1) * (UT)chunk <= trip);
+            KMP_DEBUG_ASSERT(vnew.p.ub * (UT)chunk <= trip);
             if (KMP_COMPARE_AND_STORE_REL64(
                     (volatile kmp_int64 *)&v->u.p.count,
                     *VOLATILE_CAST(kmp_int64 *) & vold.b,
                     *VOLATILE_CAST(kmp_int64 *) & vnew.b)) {
               // stealing succedded
 #ifdef KMP_DEBUG
               {
                 char *buff;