[Region analysis] Remove an assertion that doesn't always hold

It appears that we can end up breaking this assertion when inlining
SIL from modules with strict concurrency enabled into modules that
don't. That's not a assertion-worth condition.

Author: DougGregor

lib/SILOptimizer/Analysis/RegionAnalysis.cpp

@@ -3752,11 +3752,6 @@ static bool canComputeRegionsForFunction(SILFunction *fn) {
   if (!fn->getASTContext().LangOpts.hasFeature(Feature::RegionBasedIsolation))
     return false;
 
-  assert(fn->getASTContext().LangOpts.StrictConcurrencyLevel ==
-             StrictConcurrency::Complete &&
-         "Need strict concurrency to be enabled for RegionBasedIsolation to be "
-         "enabled as well");
-
   // If this function does not correspond to a syntactic declContext and it
   // doesn't have a parent module, don't check it since we cannot check if a
   // type is sendable.