minor: Only trigger PR title checker on pull requests #282

Job	Run time
ubuntu-latest/java 8-spark-3.2/java	36m 13s
macos-14(Silicon)/java 8-spark-3.4/rust	4m 0s
ubuntu-latest/java 8-spark-3.3/java	38m 17s
ubuntu-latest/java 8-spark-3.4/rust	5m 29s
ubuntu-latest/java 11-spark-3.3/java	37m 3s
macos-14(Silicon)/java 8-spark-3.4/java	29m 30s
ubuntu-latest/java 8-spark-3.4/java	37m 19s
ubuntu-latest/java 17-spark-3.3/java	35m 0s
macos-14(Silicon)/java 17-spark-3.4/rust	4m 0s
ubuntu-latest/java 17-spark-3.4/rust	5m 24s
ubuntu-latest/java 17-spark-3.4/java	35m 22s
macos-14(Silicon)/java 17-spark-3.4/java	32m 31s
macos-14(Silicon)/java 8-spark-3.2/java	26m 35s
${{ matrix.os }}/java ${{ matrix.java_version }}-spark-${{ matrix.spark-version }}/${{ matrix.test-target }}	0s
macos-14(Silicon)/java 17-spark-3.3/java	29m 0s
	5h 55m 43s

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