MDL-67673 phpunit: Remove deprecated assertEquals() params

The optional parameters of assertEquals() and assertNotEquals()
are deprecated in PHPUnit 8 (to be removed in PHPUnit 9):

- delta => use assertEqualsWithDelta()
- canonicalize => use assertEqualsCanonicalizing()
- ignoreCase => use assertEqualsIgnoringCase
- maxDepth => removed without replacement.

More info @ https://github.com/sebastianbergmann/phpunit/issues/3341

Initial search done with:

ag 'assert(Not)?Equals\(.*,.*,' --php

Then, running tests and fixing remaining cases.

lib/phpunit/tests/basic_test.php

@@ -72,7 +72,7 @@ class core_phpunit_basic_testcase extends basic_testcase {
         $this->assertNotEquals($a, $b);
         $this->assertNotEquals($a, $d);
         $this->assertEquals($a, $c);
-        $this->assertEquals($a, $b, '', 0, 10, true);
+        $this->assertEqualsCanonicalizing($a, $b);
 
         // Objects.
         $a = new stdClass();