FreeBSD 15.0 is now "PRERELEASE"

Chase URL change from the FreeBSD project.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Colin Percival <[email protected]>
Closes openzfs#17617

Author: cperciva

.github/workflows/scripts/qemu-2-start.sh

@@ -109,7 +109,7 @@ case "$OS" in
     KSRC="$FREEBSD_SNAP/../amd64/$FreeBSD/src.txz"
     ;;
   freebsd15-0c)
-    FreeBSD="15.0-CURRENT"
+    FreeBSD="15.0-PRERELEASE"
     OSNAME="FreeBSD $FreeBSD"
     OSv="freebsd14.0"
     URLxz="$FREEBSD_SNAP/$FreeBSD/amd64/Latest/FreeBSD-$FreeBSD-amd64-BASIC-CI-ufs.raw.xz"