Fix incorrect use of OCS in DCS string description.

src/conio/cterm.txt

@@ -77,7 +77,7 @@ ESC M	Reverse Line Feed (RI)
 ESC P	Device Control String (DCS)
 	Begins a string consisting of the characters 0x08 - 0x0d and
 	0x20-0x7e, terminated by a String Terminator (ST)
-	Supported OSC values:
+	Supported DCS string values:
 		"CTerm:Font:p1:<b64>"
 		Indicates the string is a loadable font. (CTerm 1.213)