ci(lintdocurls): use sed -e flag to mark argument as command #36776

Problem:
Sed thinks the argument starting with `1i` (and triple backticks) is the
suffix for the backup file because it comes right after the `-i` flag.
See for example
https://github.com/neovim/neovim/actions/runs/19774967693/job/56665991723.

Solution:
Explicitly mark it as command using the `-e` flag.

.github/workflows/lintdocurls.yml

@@ -32,7 +32,7 @@ jobs:
           make lintdocurls 2>&1 | sed -n '/invalid URLs/,/^}/p' > $OUT_FILE
           if [ -n $OUT_FILE -a -s $OUT_FILE ]; then
             # wrap output in a code block
-            sed -i '1i```' -e '$a```' $OUT_FILE
+            sed -i -e '1i```' -e '$a```' $OUT_FILE
             echo "Automatically generated on $(date) from $run_url" >> $OUT_FILE
             gh issue reopen 36597
             gh issue edit 36597 --body-file $OUT_FILE