fix: use load to slurp YAML file

[kelvintaywl]

This change leverages the load function from yq.
It allows us to load the full content from a YAML file. This way, we do not need to cat the YAML file content in a prior step.

In addition, I believe this can avoid the 'Argument list too long' yq error.
Related: https://stackoverflow.com/questions/70278587/yq-v4-env-operator-returning-errnoe2big-argument-list-too-long

I've made a sample project to showcase the proposed change.
Public workflow here:
https://app.circleci.com/pipelines/github/kelvintaywl-cci/explore-yq/2/workflows/12f05943-7c50-453b-a680-210979221316/jobs/2

additional

I confirmed that the executors have yq >= 4.x so the load function should indeed be available for the continue job (if executor is kept as default).

# docker image of orb-tools/default executor
$ docker run --rm circleci/circleci-cli:0.1.26646 yq --version
yq (https://github.com/mikefarah/yq/) version v4.31.2

# docker image of orb-tools/python executor
$ docker run --rm cimg/python:3.11 yq --version
yq (https://github.com/mikefarah/yq/) version v4.30.6

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[KyleTryon]

approving as a fix

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