Tests: Revert the case change for expected headers in HTTP tests for the 4.5 branch.

Prior to [37428], the headers returned by `wp_remote_retrieve_headers()` were case-sensitive.

Follow-up to [37428], [38730], [58008].

See #60865.

git-svn-id: https://develop.svn.wordpress.org/branches/4.5@58012 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

tests/phpunit/tests/http/functions.php

@@ -27,8 +27,8 @@ public function test_head_request() {
 		$headers = wp_remote_retrieve_headers( $response );
 
 		$this->assertInternalType( 'array', $headers, "Reply wasn't array." );
-		$this->assertSame( 'image/png', $headers['Content-Type'] );
-		$this->assertSame( '153204', $headers['Content-Length'] );
+		$this->assertSame( 'image/png', $headers['content-type'] );
+		$this->assertSame( '153204', $headers['content-length'] );
 		$this->assertSame( 200, wp_remote_retrieve_response_code( $response ) );
 	}
 
@@ -72,8 +72,8 @@ public function test_get_request() {
 
 		// Should return the same headers as a HEAD request.
 		$this->assertInternalType( 'array', $headers, "Reply wasn't array." );
-		$this->assertSame( 'image/png', $headers['Content-Type'] );
-		$this->assertSame( '153204', $headers['Content-Length'] );
+		$this->assertSame( 'image/png', $headers['content-type'] );
+		$this->assertSame( '153204', $headers['content-length'] );
 		$this->assertSame( 200, wp_remote_retrieve_response_code( $response ) );
 	}
 
@@ -94,8 +94,8 @@ public function test_get_redirect() {
 
 		// Should return the same headers as a HEAD request.
 		$this->assertInternalType( 'array', $headers, "Reply wasn't array." );
-		$this->assertSame( 'image/png', $headers['Content-Type'] );
-		$this->assertSame( '153204', $headers['Content-Length'] );
+		$this->assertSame( 'image/png', $headers['content-type'] );
+		$this->assertSame( '153204', $headers['content-length'] );
 		$this->assertSame( 200, wp_remote_retrieve_response_code( $response ) );
 	}