patch 9.0.0150: error for using #{ in an expression is a bit confusing

Problem:    Error for using #{ in an expression is a bit confusing.
Solution:   Mention that this error is only given for an expression.
            Avoid giving the error more than once. (closes #10855)
diff --git a/src/errors.h b/src/errors.h
index 3b23c88..977abbf 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -2984,8 +2984,8 @@
 	INIT(= N_("E1168: Argument already declared in the script: %s"));
 EXTERN char e_expression_too_recursive_str[]
 	INIT(= N_("E1169: Expression too recursive: %s"));
-EXTERN char e_cannot_use_hash_curly_to_start_comment[]
-	INIT(= N_("E1170: Cannot use #{ to start a comment"));
+EXTERN char e_cannot_use_hash_curly_to_start_comment_in_an_expression[]
+	INIT(= N_("E1170: Cannot use #{ to start a comment in an expression"));
 EXTERN char e_missing_end_block[]
 	INIT(= N_("E1171: Missing } after inline function"));
 EXTERN char e_cannot_use_default_values_in_lambda[]