suricata: do not run MSAN for branch 6 (#9412)

Follows #9391 to fix FPs
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=55027

projects/suricata/build.sh

@@ -82,7 +82,13 @@ then
     export RUSTFLAGS="$RUSTFLAGS -Cdebug-assertions=yes"
 fi
 
-for branch in "" 6; do
+fuzz_branches=("")
+if [[ "$SANITIZER" != "memory" ]]
+then
+    fuzz_branches+=("6")
+fi
+
+for branch in "${fuzz_branches[@]}"; do
 #we did not put libhtp there before so that cifuzz does not remove it
 cp -r libhtp suricata$branch/
 # build project