fix: Adapt to rapidyaml 0.11’s callback changes

[musicinmybrain]

Fixes #1312.

FYI, @jcpunk.

[musicinmybrain]

Testing this downstream in Fedora, combined with @jcpunk’s other recent updates and with a proposed rapidyaml 0.11.1 update, it does compile but I do still see one test failure:

59/59 Test #59: regression_test ..............................***Failed   13.12 sec
FAIL (exit code):  /builddir/build/BUILD/jsonnet-0.22.0-build/jsonnet-0.22.0/redhat-linux-build/jsonnet  --ext-str var1=test --ext-code var2='{x:1,y:2}'  error.std_parseYaml1.jsonnet
This run's output:
line=1 col=6 (5B): ERROR: [parse] two colons on same line
/builddir/build/BUILD/rapidyaml-0.11.1-build/rapidyaml-0.11.1/src/c4/yml/parse_engine.def.hpp:4140: (detected here)
Actual exit code 134, expected 1

-----------------------------

/builddir/build/BUILD/jsonnet-0.22.0-build/jsonnet-0.22.0/test_suite/run_tests.sh: FAILED: 1 / 173

I don’t really know what to make of that output.