Try to make RunningDocumentationTests platform independent

Windows seems unable to decide if the temp dir is in System32 or
system32 which breaks the comparison. This commit attempts to appease
the gods of case sensitity by reducing the portion of the path that we
check so that system32 vs System32 doesn't come into it.

See gh-8920

spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/docs/RunningDocumentationTests.java

@@ -55,9 +55,8 @@ public class RunningDocumentationTests {
 	public void bootRunSourceResources() throws IOException {
 		assertThat(this.gradleBuild
 				.script("src/main/gradle/running/boot-run-source-resources.gradle")
-				.build("configuredClasspath").getOutput()).contains(
-						new File(this.gradleBuild.getProjectDir(), "src/main/resources")
-								.getAbsolutePath());
+				.build("configuredClasspath").getOutput())
+						.contains(new File("src/main/resources").getPath());
 	}
 
 }