devops: fix Chromium clean script (#13330)

browser_patches/chromium/clean.sh

@@ -10,6 +10,6 @@ if [[ -z "${CR_CHECKOUT_PATH}" ]]; then
   CR_CHECKOUT_PATH="$HOME/chromium"
 fi
 
-if [[ ! -d "${CR_CHECKOUT_PATH}/src" ]]; then
+if [[ -d "${CR_CHECKOUT_PATH}/src" ]]; then
   rm -rf "${CR_CHECKOUT_PATH}/src/out"
 fi