docs: Specify test running prerequisites in CONTRIBUTING.md #284

	# Copyright 2023 Google LLC
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
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	name: Test Library Generation
	on:
	pull_request:
	paths-ignore:
	- "tools/**"
	- "protoc-gen-java-snowpea/**"
	- "pom.xml"
	- ".github/workflows/test_generation.yaml"

	jobs:
	test-generator:
	runs-on: ubuntu-latest
	permissions:
	contents: none

	steps:
	- run: echo "No build required."

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