Removes the GMP case from the data provider

The test is checking for exceptional situations for non-stream resources and given the other cases are more likely to run (i.e. GMP is probably not installed), it's not worth the psalm errors

Signed-off-by: George Steel <george@net-glue.co.uk>

test/StreamTest.php

@@ -4,7 +4,6 @@
 
 namespace LaminasTest\Diactoros;
 
-use GMP;
 use InvalidArgumentException;
 use Laminas\Diactoros\Stream;
 use PHPUnit\Framework\TestCase;
@@ -22,7 +21,6 @@
 use function ftok;
 use function function_exists;
 use function fwrite;
-use function gmp_init;
 use function imagecreate;
 use function is_resource;
 use function shmop_open;
@@ -624,7 +622,7 @@ public function testRaisesExceptionOnAttachForNonStreamResources(): void
         $stream->attach($resource);
     }
 
-    /** @return resource|false|GMP */
+    /** @return resource|false */
     public function getResourceFor67()
     {
         if (function_exists('curl_init')) {
@@ -635,10 +633,6 @@ public function getResourceFor67()
             return shmop_open(ftok(__FILE__, 't'), 'c', 0644, 100);
         }
 
-        if (function_exists('gmp_init')) {
-            return gmp_init(1);
-        }
-
         if (function_exists('imagecreate')) {
             return imagecreate(200, 200);
         }