rts: Fix erroneous usage of vsnprintf
As pointed out in #18685 (closed), this should be snprintf not vsnprintf. This appears to be due to a cut-and-paste error.
Fixes #18658 (closed).
As pointed out in #18685 (closed), this should be snprintf not vsnprintf. This appears to be due to a cut-and-paste error.
Fixes #18658 (closed).