Fixes HTML importer to make image entity immutable

src/model/encoding/__tests__/__snapshots__/convertFromHTMLToContentBlocks-test.js.snap

@@ -3074,6 +3074,8 @@ exports[`img with data protocol should be correctly parsed 1`] = `"\\ud83d\\udcf
 
 exports[`img with http protocol should have camera emoji content 1`] = `"\\ud83d\\udcf7"`;
 
+exports[`img with https protocol should have camera emoji content 1`] = `"\\ud83d\\udcf7"`;
+
 exports[`img with role presentation should not be rendered 1`] = `Array []`;
 
 exports[`line break should be correctly parsed - multiple <br> in a content block 1`] = `

src/model/encoding/__tests__/convertFromHTMLToContentBlocks-test.js

@@ -148,6 +148,21 @@ test('img with http protocol should have camera emoji content', () => {
     '<img src="http://www.facebook.com">',
   );
   expect(blocks.contentBlocks[0].text).toMatchSnapshot();
+  expect(
+    blocks.entityMap.__get(blocks.entityMap.__getLastCreatedEntityKey())
+      .mutability,
+  ).toBe('IMMUTABLE');
+});
+
+test('img with https protocol should have camera emoji content', () => {
+  const blocks = convertFromHTMLToContentBlocks(
+    '<img src="https://www.facebook.com">',
+  );
+  expect(blocks.contentBlocks[0].text).toMatchSnapshot();
+  expect(
+    blocks.entityMap.__get(blocks.entityMap.__getLastCreatedEntityKey())
+      .mutability,
+  ).toBe('IMMUTABLE');
 });
 
 test('img with data protocol should be correctly parsed', () => {

src/model/encoding/convertFromHTMLToContentBlocks.js

@@ -587,7 +587,7 @@ class ContentBlocksBuilder {
     // TODO: T15530363 update this when we remove DraftEntity entirely
     this.currentEntity = this.entityMap.__create(
       'IMAGE',
-      'MUTABLE',
+      'IMMUTABLE',
       entityConfig,
     );