Some test files are named without "veraPDF test suite" prefix

[shibaev]

Test files in https://github.com/veraPDF/veraPDF-corpus/tree/staging/PDF_A-1b/6.3%20Fonts/6.3.5%20Font%20subsets are named without the "veraPDF test suite " prefix.

[bdoubrov]

@shibaev thanks for noticing this, we'll fix naming of test files