ci: use ASCII release-body so Windows curl create succeeds

Git Bash on Windows mangles the UTF-8 em-dash in the create-release JSON payload,
so Gitea rejects it (422) whenever Windows is the job that creates the release.
Replace the em-dash with a plain hyphen so both platforms can create it.

.gitea/workflows/release.yml

@@ -142,7 +142,7 @@ jobs:
           REL_ID=$(curl -fsS -H "$AUTH" "${API}/releases/tags/${TAG}" \
             | grep -o '"id":[0-9]*' | head -1 | cut -d: -f2 || true)
           if [ -z "$REL_ID" ]; then
-            BODY="Gridline ${TAG#v} — Linux and Windows installers."
+            BODY="Gridline ${TAG#v} - Linux and Windows installers."
             REL_ID=$(curl -fsS -X POST -H "$AUTH" -H "Content-Type: application/json" \
               -d "{\"tag_name\":\"${TAG}\",\"name\":\"Gridline ${TAG#v}\",\"body\":\"${BODY}\",\"draft\":true}" \
               "${API}/releases" \
@@ -259,7 +259,7 @@ jobs:
           REL_ID=$(curl -fsS -H "$AUTH" "${API}/releases/tags/${TAG}" \
             | grep -o '"id":[0-9]*' | head -1 | cut -d: -f2 || true)
           if [ -z "$REL_ID" ]; then
-            BODY="Gridline ${TAG#v} — Linux and Windows installers."
+            BODY="Gridline ${TAG#v} - Linux and Windows installers."
             REL_ID=$(curl -fsS -X POST -H "$AUTH" -H "Content-Type: application/json" \
               -d "{\"tag_name\":\"${TAG}\",\"name\":\"Gridline ${TAG#v}\",\"body\":\"${BODY}\",\"draft\":true}" \
               "${API}/releases" \