patch 8.2.0773: switching to raw mode every time ":" is used

Problem:    Switching to raw mode every time ":" is used.
Solution:   When executing a shell set cur_tmode to TMODE_UNKNOWN, so that the
            next time TMODE_RAW is used it is set, but not every time.
diff --git a/src/term.c b/src/term.c
index 9803a1b..1260c9a 100644
--- a/src/term.c
+++ b/src/term.c
@@ -2862,7 +2862,7 @@
 #if defined(FEAT_VTP) && defined(FEAT_TERMGUICOLORS)
 		  || (s[0] == ESC && s[1] == '|')
 #endif
-	          || (s[0] == CSI && (i = 1) == 1))
+		  || (s[0] == CSI && (i = 1) == 1))
 	      && s[i] != NUL
 	      && (STRCMP(s + i + 1, "%p1%dm") == 0
 		  || STRCMP(s + i + 1, "%dm") == 0)
@@ -3447,14 +3447,14 @@
     if (full_screen)
     {
 	/*
-	 * When returning after calling a shell we want to really set the
-	 * terminal to raw mode, even though we think it already is, because
-	 * the shell program may have reset the terminal mode.
+	 * When returning after calling a shell cur_tmode is TMODE_UNKNOWN,
+	 * set the terminal to raw mode, even though we think it already is,
+	 * because the shell program may have reset the terminal mode.
 	 * When we think the terminal is normal, don't try to set it to
 	 * normal again, because that causes problems (logout!) on some
 	 * machines.
 	 */
-	if (tmode != TMODE_COOK || cur_tmode != TMODE_COOK)
+	if (tmode != cur_tmode)
 	{
 #ifdef FEAT_TERMRESPONSE
 # ifdef FEAT_GUI