patch 8.2.3961: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/blob.c b/src/blob.c
index 9d41bdc..37d2be6 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -614,7 +614,7 @@
 	    return;		// type error; errmsg already given
 	if (before < 0 || before > len)
 	{
-	    semsg(_(e_invarg2), tv_get_string(&argvars[2]));
+	    semsg(_(e_invalid_argument_str), tv_get_string(&argvars[2]));
 	    return;
 	}
     }
@@ -623,7 +623,7 @@
 	return;
     if (val < 0 || val > 255)
     {
-	semsg(_(e_invarg2), tv_get_string(&argvars[1]));
+	semsg(_(e_invalid_argument_str), tv_get_string(&argvars[1]));
 	return;
     }