patch 8.2.0967: unnecessary type casts for vim_strnsave()

Problem:    Unnecessary type casts for vim_strnsave().
Solution:   Remove the type casts.
diff --git a/src/term.c b/src/term.c
index 2f6e893..82b1126 100644
--- a/src/term.c
+++ b/src/term.c
@@ -4086,11 +4086,11 @@
     }
 
 #if defined(MSWIN) && !defined(FEAT_GUI)
-    s = vim_strnsave(string, (int)STRLEN(string) + 1);
+    s = vim_strnsave(string, STRLEN(string) + 1);
 #else
 # ifdef VIMDLL
     if (!gui.in_use)
-	s = vim_strnsave(string, (int)STRLEN(string) + 1);
+	s = vim_strnsave(string, STRLEN(string) + 1);
     else
 # endif
 	s = vim_strsave(string);