MDL-83634 tool_brickfield: Increase the alt text limit to 750 characters

This is consistent with the alt-text length limit of 750 characters in
Moodle's editor.

Author: junpataleta

admin/tool/brickfield/classes/local/htmlchecker/common/checks/img_alt_is_too_long.php

@@ -37,7 +37,7 @@ public function check(): void {
         global $alttextlengthlimit;
 
         foreach ($this->get_all_elements('img') as $img) {
-            $alttextlengthlimit = 125;
+            $alttextlengthlimit = 750;
             if ($img->hasAttribute('alt') && core_text::strlen($img->getAttribute('alt')) > $alttextlengthlimit) {
                 $this->add_report($img);
             }

admin/tool/brickfield/tests/local/htmlchecker/common/checks/img_alt_is_too_long_test.php

@@ -64,21 +64,21 @@ protected function get_test_html(string $alttext): string {
      */
     public static function img_alt_text_provider(): array {
         return [
-            'Alt text <= 125 characters' => [
+            'Alt text <= 750 characters' => [
                 true,
-                str_repeat("Hello world!", 10),
+                str_repeat("Hello world!", 60),
             ],
-            'Alt text > 125 characters' => [
+            'Alt text > 750 characters' => [
                 false,
-                str_repeat("Hello world!", 25),
+                str_repeat("Hello world!", 65),
             ],
-            'Multi-byte alt text <= 125 characters' => [
+            'Multi-byte alt text <= 750 characters' => [
                 true,
-                str_repeat('こんにちは、世界！', 13),
+                str_repeat('こんにちは、世界！', 83),
             ],
-            'Multi-byte alt text > 125 characters' => [
+            'Multi-byte alt text > 750 characters' => [
                 false,
-                str_repeat('こんにちは、世界！', 30),
+                str_repeat('こんにちは、世界！', 90),
             ],
         ];
     }
@@ -96,7 +96,7 @@ public function test_check(bool $expectedpass, string $alttext): void {
         if ($expectedpass) {
             $this->assertEmpty($results);
         } else {
-            $this->assertTrue($results[0]->element->tagName === 'img');
+            $this->assertEquals('img', $results[0]->element->tagName);
         }
     }
 }