travis_get_script: Adapt to pyyaml version bump in latest image - #503

This should reduce the number of failing jobs from 24 (https://buildkite.com/dlang/dmd/builds/49125/list?sid=01a07b93-92d3-4780-b739-3c7562d8bfcd&tab=output) to 5 (https://buildkite.com/dlang/ci/builds/976/list?jid=01a07bb6-cf3d-471b-9b73-f2544725fe96&tab=output). Out of these 5 remaining failures:

• 2 Tsunami jobs seem to require https://packages.ubuntu.com/noble/libpcre3-dev (Buildkite runtime image lacks pcre library #502)
• autowrap and dstep seem to require a libclang-dev (/usr/bin/ld: cannot find -lclang: No such file or directory / object.Exception@configure.d(369): Could not find libclang.so in any of the standard paths for llvm).
  Edit: libclang-dev is installed, but seems like the 2 projects don't find it by default.
• dlang-tour/core might require a bump for the libssl bindings:

../.dub/packages/openssl/3.3.0/openssl/source/deimos/openssl/opensslv.di(85,9): Error: static assert:  `-45 >= 0` is false
        static assert (build >= 0);