[vscode-pyspark] typo statefulset.yaml

[JackLemaitre]

Description of the change

mdir -> mkdir
fix bug of the creation of the spark-default.conf which must be a file and not a directory

Checklist

• [ x] Chart version bumped in Chart.yaml
• [x ] Title of the pull request follows this pattern [name_of_the_chart] Descriptive title

[ihiverlet]

thanks !