fix plpython2u's RSS numbers

Author: NikolayS

benchmarks.md

@@ -173,7 +173,7 @@ Method | Latency, ms | TPS | RSS
 pgsql-http (C) | 235.92 | 42.39 | ~24MB
 plsh (curl) | 306.95 | 32.58 | ~30MB (19324+3288+7732)
 plpython2u | 233.74 | 42.79 | ~30MB
-plpython3u | 234.20 | 42.70 | ~30MB
+plpython3u | 234.20 | 42.70 | ~32MB
 
 The "plsh" approach has an obvious drawback: additional separate `curl` process is to be invoked for every query. 
 As a result, it shows slower results compared to [pgsql-http](https://github.com/pramsey/pgsql-http)