[Concurrency] reformat help message for SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE

Author: ktoso

stdlib/public/runtime/EnvironmentVariables.def

@@ -126,10 +126,9 @@ VARIABLE(SWIFT_IS_CURRENT_EXECUTOR_LEGACY_MODE_OVERRIDE, string, "",
          "implemented SerialExecutor.checkIsolation which should crash if the "
          "isolation is not the expected one. Some old code may rely on the "
          "non-crashing behavior. This flag enables temporarily restoring the "
-         "legacy 'nocrash' behavior until adopting code has been adjusted.\n"
-         "\n"
-         "Legal values are: \n"
-         "  - nocrash (Legacy behavior)\n"
-         "  - crash (Swift 6.0+ behavior)")
+         "legacy 'nocrash' behavior until adopting code has been adjusted. "
+         "Legal values are: "
+         " 'nocrash' (Legacy behavior), "
+         " 'crash' (Swift 6.0+ behavior)")
 
 #undef VARIABLE