patch 8.2.3960: 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 1387a8e..9d41bdc 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -399,7 +399,7 @@
 
     if (n2 - n1 + 1 != blob_len(src->vval.v_blob))
     {
-	emsg(_("E972: Blob value does not have the right number of bytes"));
+	emsg(_(e_blob_value_does_not_have_right_number_of_bytes));
 	return FAIL;
     }