minor #37773 Modernized deprecated PHPUnit assertion calls (derrabus)

This PR was squashed before being merged into the 3.4 branch.

Discussion
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Modernized deprecated PHPUnit assertion calls

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | Part of #37564
| License       | MIT
| Doc PR        | N/A

Some assertions have been renamed in PHPUnit 9. PhpUnitBridge should already have polyfills in place for those methods, so it should be save to use them.

Commits
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ab417f7040 Modernized deprecated PHPUnit assertion calls

Author: fabpot

Http/Tests/EntryPoint/DigestAuthenticationEntryPointTest.php

@@ -31,7 +31,7 @@ public function testStart()
         $response = $entryPoint->start($request, $authenticationException);
 
         $this->assertEquals(401, $response->getStatusCode());
-        $this->assertRegExp('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}"$/', $response->headers->get('WWW-Authenticate'));
+        $this->assertMatchesRegularExpression('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}"$/', $response->headers->get('WWW-Authenticate'));
     }
 
     public function testStartWithNoException()
@@ -42,7 +42,7 @@ public function testStartWithNoException()
         $response = $entryPoint->start($request);
 
         $this->assertEquals(401, $response->getStatusCode());
-        $this->assertRegExp('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}"$/', $response->headers->get('WWW-Authenticate'));
+        $this->assertMatchesRegularExpression('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}"$/', $response->headers->get('WWW-Authenticate'));
     }
 
     public function testStartWithNonceExpiredException()
@@ -55,6 +55,6 @@ public function testStartWithNonceExpiredException()
         $response = $entryPoint->start($request, $nonceExpiredException);
 
         $this->assertEquals(401, $response->getStatusCode());
-        $this->assertRegExp('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}", stale="true"$/', $response->headers->get('WWW-Authenticate'));
+        $this->assertMatchesRegularExpression('/^Digest realm="TheRealmName", qop="auth", nonce="[a-zA-Z0-9\/+]+={0,2}", stale="true"$/', $response->headers->get('WWW-Authenticate'));
     }
 }