[stable/percona] Fix README to match default persistence settings (#1133)
[stable/percona] Fix README to match default persistence settings (#1133)

The README for the Percona chart claims that persistence is enabled by
default, but `persistence.enabled` defaults to `false` in `values.yaml`.

Fixes #1128.
barklyprotects/charts,mlaccetti/charts,mluedke/charts,GaneshSPatil/charts,trobert2/charts-1,kachkaev/charts,smileisak/charts,smelchior/charts,GaneshSPatil/charts,eicnix/charts,grugnog/charts,rimusz/helm-charts,eicnix/charts,viglesiasce/charts,grugnog/charts,mlaccetti/charts,eicnix/charts,trobert2/charts-1,rimusz/helm-charts,viglesiasce/charts,mluedke/charts,mluedke/charts,viglesiasce/charts,samisms/charts,smileisak/charts,smelchior/charts,caiwenhao/charts,lachie83/charts,sd2k/charts,rimusz/helm-charts,oleh-ozimok/charts,escardin/charts,smileisak/charts,oleh-ozimok/charts,helm/charts,trobert2/charts-1,lachie83/charts,kachkaev/charts,barklyprotects/charts,escardin/charts,oleh-ozimok/charts,ledor473/charts,sd2k/charts,grugnog/charts,smelchior/charts,escardin/charts,helm/charts,ledor473/charts,samisms/charts,GaneshSPatil/charts,helm/charts,ledor473/charts,jainishshah17/charts,jainishshah17/charts,sstarcher/charts,samisms/charts,mlaccetti/charts,caiwenhao/charts,helm/charts,sstarcher/charts,lachie83/charts,sstarcher/charts,kachkaev/charts,sd2k/charts,sd2k/charts,jainishshah17/charts,GaneshSPatil/charts,caiwenhao/charts,lachie83/charts,rimusz/helm-charts,barklyprotects/charts