Tests: Minimize the chances of signature conflicts for assertEqualsWithDelta().

The PHPUnit 7.5+ method `assertEqualsWithDelta()` was polyfilled for PHPUnit < 7.5, but also overloaded for PHPUnit 7.5 itself, which was not necessary and created a higher chance of signature conflicts, especially when the WP test suite is used as a basis for integration tests with plugins/themes.

This change removes the unnecessary overloading for PHPUnit 7.5+ and simplifies the overloaded method for PHPUnit < 7.5, including removing the `IsEqual()` class alias declaration, no longer needed.

Follow-up to [48952].

Props jrf.
See #52625.

git-svn-id: https://develop.svn.wordpress.org/trunk@50986 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/includes/phpunit7/testcase.php

@@ -11,30 +11,4 @@ require_once dirname( __DIR__ ) . '/abstract-testcase.php';
  *
  * All WordPress unit tests should inherit from this class.
  */
-class WP_UnitTestCase extends WP_UnitTestCase_Base {
-
-	/**
-	 * Asserts that two variables are equal (with delta).
-	 *
-	 * This method has been backported from a more recent PHPUnit version,
-	 * as tests running on PHP 5.6 use PHPUnit 5.7.x.
-	 *
-	 * @since 5.6.0
-	 *
-	 * @param mixed  $expected First value to compare.
-	 * @param mixed  $actual   Second value to compare.
-	 * @param float  $delta    Allowed numerical distance between two values to consider them equal.
-	 * @param string $message  Optional. Message to display when the assertion fails.
-	 *
-	 * @throws ExpectationFailedException
-	 * @throws \SebastianBergmann\RecursionContext\InvalidArgumentException
-	 */
-	public static function assertEqualsWithDelta( $expected, $actual, float $delta, string $message = '' ): void {
-		$constraint = new PHPUnit\Framework\Constraint\IsEqual(
-			$expected,
-			$delta
-		);
-
-		static::assertThat( $actual, $constraint, $message );
-	}
-}
+class WP_UnitTestCase extends WP_UnitTestCase_Base {}