fix docs

docs/installation/otp_en.md

@@ -134,7 +134,7 @@ su pleroma -s $SHELL -lc "./bin/pleroma_ctl migrate"
 # su pleroma -s $SHELL -lc "./bin/pleroma_ctl migrate --migrations-path priv/repo/optional_migrations/rum_indexing/"
 
 # Start the instance to verify that everything is working as expected
-su pleroma -s $SHELL -lc "export $( cat /opt/pleroma/config/pleroma.env | xargs); ./bin/pleroma daemon"
+su pleroma -s $SHELL -lc "export $(cat /opt/pleroma/config/pleroma.env); ./bin/pleroma daemon"
 
 # Wait for about 20 seconds and query the instance endpoint, if it shows your uri, name and email correctly, you are configured correctly
 sleep 20 && curl http://localhost:4000/api/v1/instance