Fix java.nio.file import in AutoCloseable example

[HyukjinKwon]

This PR proposes to fix the import in AutoCloseable example. The current example fails as below:

>>> from java.nio.files import Files, Paths

Traceback (most recent call last):
  File "org.jpype.JPypeContext.java", line -1, in org.jpype.JPypeContext.callMethod
  ...
java.lang.ClassNotFoundException: java.lang.ClassNotFoundException: java.nio.files
  ...
ImportError: Failed to import 'java.nio.files'

It has to be java.nio.file:

>>> from java.nio.file import Files, Paths

[codecov]

Codecov Report

Merging #1021 (4b0c837) into master (bbdca90) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1021   +/-   ##
=======================================
  Coverage   89.10%   89.11%           
=======================================
  Files         112      112           
  Lines       10041    10041           
  Branches     3972     3972           
=======================================
+ Hits         8947     8948    +1     
  Misses        658      658           
+ Partials      436      435    -1     

Impacted Files	Coverage Δ
native/common/include/jp_primitive_accessor.h	74.16% <0.00%> (+0.83%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bbdca90...4b0c837. Read the comment docs.