bug#51447: Guile-gi fails a few tests on core-updates-frozen

[Vivien Kraus]

Dear guix,

For my program, I depend on guile-gi. However, the test/string.scm test
contains some characters that are not recognized by guile (I suggest
using (call-with-input-string "<the character>" read-char) instead of
#\<the character>), and once that’s fixed, more tests fail, for which I
have no solution.

Best regards,

Vivien