[COLLECTIONS-812] fix flaky test due to timestamp comment inserted in…

[samabcde]

… Properties methods.

A comment line is inserted after the comment given when using Properties#save(OutputStream, String), Properties#store(OutputStream, String) and Properties#store(Writer, String)
e.g.#Sat Apr 30 22:00:30 HKT 2022. Hence the test will fail when actual, expected content are not written in same second. To fix the problem, comparison will ignore this comment

• Additional to [COLLECTIONS-812] Open both streams with try-with-resources, and assert that only the text is the same, not the time #305, also fix testStoreToPrintWriter() and testSetProperty() which are also using Properties#store

• Remove unnecessary throws IOException

@kinow, should we keep using Properties#save for compatibility, or just use Properties#store and rename the method to testStore?

[kinow]

Superseded by #305 , I think :-)

[samabcde]

@kinow , see your fix after I completed this, so I will close this PR. But please help to fix testStoreToOutputStream() and testStoreToPrintWriter() which are also using Properties#store and hence are also flaky.