Remove outdated Maven requirement from README
Remove outdated Maven requirement from README

We use `./mvnw`, so Maven is not required.

martint/presto,martint/presto,martint/presto,treasure-data/presto,dain/presto,dain/presto,losipiuk/presto,treasure-data/presto,electrum/presto,smartnews/presto,erichwang/presto,hgschmie/presto,11xor6/presto,treasure-data/presto,Praveen2112/presto,losipiuk/presto,treasure-data/presto,electrum/presto,martint/presto,Praveen2112/presto,losipiuk/presto,ebyhr/presto,erichwang/presto,11xor6/presto,hgschmie/presto,Praveen2112/presto,hgschmie/presto,hgschmie/presto,ebyhr/presto,losipiuk/presto,Praveen2112/presto,electrum/presto,wyukawa/presto,wyukawa/presto,dain/presto,11xor6/presto,wyukawa/presto,electrum/presto,erichwang/presto,ebyhr/presto,losipiuk/presto,martint/presto,wyukawa/presto,ebyhr/presto,dain/presto,smartnews/presto,treasure-data/presto,smartnews/presto,11xor6/presto,hgschmie/presto,dain/presto,treasure-data/presto,Praveen2112/presto,11xor6/presto,smartnews/presto,ebyhr/presto,erichwang/presto,smartnews/presto,wyukawa/presto,electrum/presto,erichwang/presto