[Dexter] Remove debugger-dependent test from windows

One of the tests added in the recent floating point patch involves
string comparison against the debugger output; as DbgEng and LLDB have
different output, the test cannot pass against both of them, so disable
it on windows.

cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/perfect/float_range_watch/float_range_no_arg.cpp

@@ -3,7 +3,9 @@
 //      the floating point range evalution and defaults back to
 //      pre-float evalution.
 //
-// UNSUPPORTED: system-darwin
+// Since this test involves string comparison to the debugger output, it cannot
+// work for both dbgeng and lldb, which output floats differently.
+// UNSUPPORTED: system-darwin, system-windows
 //
 // RUN: %dexter_regression_test -- %s | FileCheck %s
 // CHECK: float_range_no_arg.cpp: