doc: rename defaultEncoding option to encoding
The documentation for fs.createWriteStream() references a
defaultEncoding as possible options property, but in reality
encoding property is expected and properly handled. This fix updates
the documentation to rename the defaultEncoding property to
encoding.
Fixes: https://github.com/nodejs/node/issues/14611
Checklist
-
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc