[flang] disable memory-allocation-opt.fir test on windows (#83535)

It is randomly failing in windows pre-merge checks and causing noise in
Github PRs.

Not clear why it is crashing on windows, issue opened:
#83534

Author: jeanPerier

flang/test/Fir/memory-allocation-opt.fir

@@ -1,4 +1,6 @@
 // RUN: fir-opt --memory-allocation-opt="dynamic-array-on-heap=true maximum-array-alloc-size=1024" %s | FileCheck %s
+// FIXME: started crashing on windows https://github.com/llvm/llvm-project/issues/83534
+// UNSUPPORTED: system-windows
 
 // Test for size of array being too big.