Remove pgrust: the entry is cheating

A pgrust database entry is being removed from the ClickBench benchmark because it violates competition rules through two forms of cheating: it embeds hand-written kernels specifically optimized for each of the 43 benchmark queries, and its "hot runs" replay cached results from previous executions rather than performing actual queries. The entry was also falsely tagged as untuned despite being heavily customized for these exact queries, with evidence including hardcoded query plans, metadata-only answers for certain queries, and explicit result caching mechanisms in the code.