DOC: fix missing closing brackend on regsub
"]" was missing for <flags>.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 60d1df2..3cf54e4 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -10365,7 +10365,7 @@
| `---------------------------- key
`------------------------------------ leading spaces ignored
-regsub(<regex>,<subst>[,<flags>)
+regsub(<regex>,<subst>[,<flags>])
Applies a regex-based substitution to the input string. It does the same
operation as the well-known "sed" utility with "s/<regex>/<subst>/". By
default it will replace in the input string the first occurrence of the