[1.5.x] Updated our six module to follow upstream changes.

This includes fixes for the java/jython detection and a new license header.

Thanks to Thomas Bartelmess for the report.

Backport of c5ce0e8a687ecf7fbc38fa85c5311a6320a246c6 from master.
[1.5.x] Updated bundled version of six.

Backport of e11ccc76d325b6bbbf101f510a91299f507f0745.
[1.5.x] Stopped using non-standard __globals__ and __code__ attributes.

Some alternative implementations don't have them.

Closes #19944.

Backport of 9d4a5b00f1977d8cddf8e241fa4bb8a9e819f188 from master.