Try to fix flatpak upload

.ci/upload-nightly-gitlab.sh

@@ -3,7 +3,7 @@
 file="$1"
 fileName="nheko-${CI_COMMIT_REF_NAME}-${CI_COMMIT_SHORT_SHA}-${file##*-}"
 
-uri=$(curl -H "Authorization: Bearer ${MATRIX_ACCESS_TOKEN}" -H "Content-Type: application/x-compressed" -X POST --data-binary "@${file}" "https://matrix.neko.dev/_matrix/media/r0/upload?filename=${fileName}"  --http1.1 | python -c "import sys, json; print(json.load(sys.stdin)['content_uri'])")
+uri=$(curl -H "Authorization: Bearer ${MATRIX_ACCESS_TOKEN}" -H "Content-Type: application/x-compressed" -X POST --data-binary "@${file}" "https://matrix.neko.dev/_matrix/media/r0/upload?filename=${fileName}"  --http1.1 | python3 -c "import sys, json; print(json.load(sys.stdin)['content_uri'])")
 echo "Uploaded to ${uri}"
 
 curl -H "Authorization: Bearer ${MATRIX_ACCESS_TOKEN}" -H "Content-Type: application/json" -X PUT -d "{ \"body\": \"${fileName}\", \"filename\": \"${fileName}\", \"info\": { \"mimetype\": \"application/x-compressed\", \"size\": $(wc -c < ${file}) }, \"msgtype\": \"m.file\", \"url\": \"${uri}\" }" "https://matrix.neko.dev/_matrix/client/r0/rooms/${ROOM}/send/m.room.message/$(date +%s)"