testing/pdfjs: switch to legacy version and strip
Qt5Webengine is not compatible with some fancy js stuff on last version so I need to pick the legacy version.
I removed the pdf file (why is that there?) and the '*.js.map' files as they seem only useful for debugging purposes.
I tested it removing all the fonts and cbmap files. It worked fine for few documents but complained about missing 'FoxitSymbol.pfb', so better let them there for now.