patch 8.2.4005: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 2af1f56..b394342 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -1612,8 +1612,8 @@
 
 			      if (i < 0 || i > INT_MAX)
 				  EMSG2_RET_NULL(
-					_("E678: Invalid character after %s%%[dxouU]"),
-					reg_magic == MAGIC_ALL);
+					    _(e_invalid_character_after_str_2),
+						       reg_magic == MAGIC_ALL);
 			      if (use_multibytecode(i))
 				  ret = regnode(MULTIBYTECODE);
 			      else