Remove duplicate ExploitAssigns test

[CamWass]

The test case test("a = !0; b = !0", "b = a = !0"); occurs in testExprExploitationTypes2 and also above that in testExprExploitationTypes, on line 30:

closure-compiler/test/com/google/javascript/jscomp/ExploitAssignsTest.java

Lines 28 to 30 in c0ae6b5

	public void testExprExploitationTypes() {
	test("a = true; b = true", "b = a = true");
	test("a = !0; b = !0", "b = a = !0");

[lauraharker]

Thanks for the cleanup!