vsl: Fold Backend_health window bits docs

The net result is the same, but should be more readable.

Better diff with the --word-diff --word-diff-regex=. options.

include/tbl/vsl_tags.h

@@ -455,15 +455,15 @@ SLTM(Backend_health, 0, "Backend health check",
 	"\n"
 
 	"Probe window bits are::\n\n"
-	"\t" "'-'" ": " "Could not connect" "\n"
-	"\t" "'4'" ": " "Good IPv4" "\n"
-	"\t" "'6'" ": " "Good IPv6" "\n"
-	"\t" "'U'" ": " "Good UNIX" "\n"
-	"\t" "'x'" ": " "Error Xmit" "\n"
-	"\t" "'X'" ": " "Good Xmit" "\n"
-	"\t" "'r'" ": " "Error Recv" "\n"
-	"\t" "'R'" ": " "Good Recv" "\n"
-	"\t" "'H'" ": " "Happy" "\n"
+	"\t'-': Could not connect\n"
+	"\t'4': Good IPv4\n"
+	"\t'6': Good IPv6\n"
+	"\t'U': Good UNIX\n"
+	"\t'x': Error Xmit\n"
+	"\t'X': Good Xmit\n"
+	"\t'r': Error Recv\n"
+	"\t'R': Good Recv\n"
+	"\t'H': Happy\n"
 	"\n"
 	"When the backend is just created, the window bits for health check\n"
 	"slots that haven't run yet appear as '-' like failures to connect.\n"