Tweak file property of import control config to work on Windows

spring-boot-parent/src/checkstyle/checkstyle.xml

@@ -78,7 +78,7 @@
 			<property name="processJavadoc" value="true" />
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.ImportControlCheck">
-			<property name="file" value="file://${main.basedir}/spring-boot-parent/src/checkstyle/import-control.xml" />
+			<property name="file" value="${main.basedir}/spring-boot-parent/src/checkstyle/import-control.xml" />
 			<property name="path" value="^.*[\\/]src[\\/]main[\\/].*$" />
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck">