Drop a REQUIRES: lldb on a dexter regression test

As this is a test that actually gets to operating the debugger, it
needs to be limited to scenarios where the debugger is available.

(We'll file this in the set of things Dexter doesn't handle gracefully..)

GitOrigin-RevId: 7deb970efb0f1a7ccb04740710f683e00e005eae
diff --git a/dexter/feature_tests/subtools/test/label_another_line.cpp b/dexter/feature_tests/subtools/test/label_another_line.cpp
index c6284ef..3067617 100644
--- a/dexter/feature_tests/subtools/test/label_another_line.cpp
+++ b/dexter/feature_tests/subtools/test/label_another_line.cpp
@@ -1,3 +1,6 @@
+// REQUIRES: lldb
+// UNSUPPORTED: system-windows
+//
 // Purpose:
 //    Check that the optional keyword argument 'on_line' makes a \DexLabel label
 //    that line instead of the line the command is found on.