Fix JUnit 5 migration issues in org.eclipse.text.tests

This commit fixes test failures introduced during the JUnit 5 migration
in PR #3410 for the org.eclipse.text.tests bundle.

Changes:
1. Added missing JUnit 5 package import to MANIFEST.MF:
   - org.junit.jupiter.api.function (required for assertThrows)

2. Fixed assertEquals parameter order in TextEditTests.java:
   - JUnit 5 changed assertEquals signature from (message, expected, actual)
     to (expected, actual, message)
   - Fixed 61 assertions to use correct JUnit 5 parameter order

3. Fixed annotation in FindReplaceDocumentAdapterTest.java:
   - Changed @org.junit.Test (JUnit 4) to @test (JUnit 5)
   - This was preventing @beforeeach from running, causing null pointer errors

All 578 tests now pass successfully (0 failures, 0 errors, 2 skipped).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: 2 people

tests/org.eclipse.text.tests/META-INF/MANIFEST.MF

@@ -15,6 +15,7 @@ Require-Bundle:
  org.eclipse.text;bundle-version="[3.6.3,4.0.0)",
  org.junit;bundle-version="4.12.0"
 Import-Package: org.junit.jupiter.api;version="[5.14.0,6.0.0)",
+ org.junit.jupiter.api.function;version="[5.14.0,6.0.0)",
  org.junit.platform.suite.api;version="[1.14.0,2.0.0)"
 Bundle-RequiredExecutionEnvironment: JavaSE-17
 Eclipse-BundleShape: dir

tests/org.eclipse.text.tests/src/org/eclipse/text/tests/FindReplaceDocumentAdapterTest.java

@@ -77,7 +77,7 @@ public void tearDown () {
 		fDocument= null;
 	}
 
-	@org.junit.Test
+	@Test
 	public void testFind() {
 		FindReplaceDocumentAdapter findReplaceDocumentAdapter= new FindReplaceDocumentAdapter(fDocument);
 		try {