Correct minor typo in exception message

* Correct a minor typo in the exception message that responds to a
  failed attempt to add a folder to the Java source path which is
  already implicitly included by one of its parents

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/ProjectUtils.java

@@ -172,7 +172,7 @@ public static boolean addSourcePath(IPath sourcePath, IPath[] exclusionPaths, IJ
 
 		if (!parentSrcPaths.isEmpty()) {
 			throw new CoreException(new Status(IStatus.ERROR, IConstants.PLUGIN_ID, Messages
-					.format("Cannot add the folder ''{0}'' to the source path because it''s parent folder is already in the source path of the project ''{1}''.", new String[] { sourcePath.toOSString(), project.getProject().getName() })));
+					.format("Cannot add the folder ''{0}'' to the source path because its parent folder is already in the source path of the project ''{1}''.", new String[] { sourcePath.toOSString(), project.getProject().getName() })));
 		}
 
 		if (exclusionPaths != null) {