Tests: Correct the slowThreshold option name for SpeedTrapListener.

The previous change in [45607] appears to be accidental.

Props Rarst.
Fixes #48933.

git-svn-id: https://develop.svn.wordpress.org/trunk@46881 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

phpunit.xml.dist

@@ -33,7 +33,7 @@
 		<listener class="SpeedTrapListener" file="tests/phpunit/includes/listener-loader.php">
 			<arguments>
 				<array>
-					<element key="slow_threshold">
+					<element key="slowThreshold">
 						<integer>150</integer>
 					</element>
 				</array>