user-agent.md: mention double quotes too

Reported-by: Jeremy Nicoll
Bug: https://curl.se/mail/archive-2026-04/0029.html
Closes #21477

diff --git a/docs/cmdline-opts/user-agent.md b/docs/cmdline-opts/user-agent.md
index a24bd28449ad80b152a46ebb65761bac3ae0efc6..d81b65d34fa43eba8e99370765ddf56175fe0bcd 100644 (file)
--- a/docs/cmdline-opts/user-agent.md
+++ b/docs/cmdline-opts/user-agent.md
@@ -19,8 +19,8 @@ Example:
 # `--user-agent`
 
 Specify the User-Agent string to send to the HTTP server. To encode blanks in
-the string, surround the string with single quote marks. This header can also
-be set with the --header or the --proxy-header options.
+the string, surround the string with single or double quote marks. This header
+can also be set with the --header or the --proxy-header options.
 
 If you give an empty argument to --user-agent (""), it removes the header
 completely from the request. If you prefer a blank header, you can set it to a