patch 8.2.3461: cannot distinguish Normal and Terminal-Normal mode

Problem:    Cannot distinguish Normal and Terminal-Normal mode.
Solution:   Make mode() return "nt" for Terminal-Normal mode. (issue #8856)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 00ba2e4..43aae40 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -8061,7 +8061,7 @@
 		returned, otherwise only the first letter is returned.
 		Also see |state()|.
 
-		   n	    Normal, Terminal-Normal
+		   n	    Normal
 		   no	    Operator-pending
 		   nov	    Operator-pending (forced characterwise |o_v|)
 		   noV	    Operator-pending (forced linewise |o_V|)
@@ -8070,6 +8070,7 @@
 		   niI	    Normal using |i_CTRL-O| in |Insert-mode|
 		   niR	    Normal using |i_CTRL-O| in |Replace-mode|
 		   niV	    Normal using |i_CTRL-O| in |Virtual-Replace-mode|
+		   nt	    Terminal-Normal (insert goes to Terminal-Job mode)
 		   v	    Visual by character
 		   V	    Visual by line
 		   CTRL-V   Visual blockwise