chore: Interpret git log grep pattern as literal string (#264)

## Motivation

Commits which had special regex characters, like square braces, were
causing the `git log --grep <pattern>` to fail.
We need to interpret these as literal strings, thus `-F` flag, which as
per `man git log` says:
> -F, --fixed-strings
Consider the limiting patterns to be fixed strings (don’t interpret
pattern as a regular expression).

.github/scripts/release-notes.sh

@@ -55,7 +55,7 @@ while IFS= read -r line; do
 		continue
 	fi
 	commit_msg="${BASH_REMATCH[1]}"
-	commit_body=$(git log --grep "$commit_msg" -n1 --pretty="%b")
+	commit_body=$(git log -F --grep "$commit_msg" -n1 --pretty="%b")
 
 	add_notes() {
 		local notes="$1"