remove java test EmptyInterface

This is a test of an internal query for the Semmle repository. It cannot
run against the public QL repository alone, and therefore should not be
tested here.

https://git.semmle.com/Semmle/code/pull/35690 adds the test back to the
internal repo.

java/ql/test/query-tests/EmptyInterface/EmptyInterface.expected

@@ -1,3 +0,0 @@
-| IAmBad.java:1:18:1:23 | IAmBad | Do not use empty interfaces; put some of the behavior in the interface or (better) an abstract superclass. |
-| IAmBadAsWell.java:1:18:1:29 | IAmBadAsWell | Do not use empty interfaces; put some of the behavior in the interface or (better) an abstract superclass. |
-| IAmBadToo.java:1:18:1:26 | IAmBadToo | Do not use empty interfaces; put some of the behavior in the interface or (better) an abstract superclass. |

java/ql/test/query-tests/EmptyInterface/EmptyInterface.qlref

@@ -1 +0,0 @@
-general/EmptyInterface.ql

java/ql/test/query-tests/EmptyInterface/IAmAlsoOK.java

@@ -1 +0,0 @@
-public interface IAmAlsoOK extends java.util.Collection<Number> {}

java/ql/test/query-tests/EmptyInterface/IAmBad.java

@@ -1 +0,0 @@
-public interface IAmBad {}

java/ql/test/query-tests/EmptyInterface/IAmBadAsWell.java

@@ -1 +0,0 @@
-public interface IAmBadAsWell {}

java/ql/test/query-tests/EmptyInterface/IAmBadToo.java

@@ -1 +0,0 @@
-public interface IAmBadToo extends IAmBad {}

java/ql/test/query-tests/EmptyInterface/IAmNonEmpty.java

@@ -1,3 +0,0 @@
-public interface IAmNonEmpty {
-	public void m();
-}

java/ql/test/query-tests/EmptyInterface/IAmNonEmptyAsWell.java

@@ -1,5 +0,0 @@
-public interface IAmNonEmptyAsWell {
-	public class C {
-		int x;
-	}
-}

java/ql/test/query-tests/EmptyInterface/IAmNonEmptyToo.java

@@ -1,3 +0,0 @@
-public interface IAmNonEmptyToo {
-	public String hello = "world";
-}

java/ql/test/query-tests/EmptyInterface/IAmOK.java

@@ -1 +0,0 @@
-public interface IAmOK extends IAmBad, IAmBadToo {}

java/ql/test/query-tests/EmptyInterface/IAmUseful.java

@@ -1 +0,0 @@
-public @interface IAmUseful {}