Update jest-diff to remove colors from no diff message

Updates to the latest jest-diff which now supports removing color codes
from "no visual difference" message. A test has been added to confirm
this and prevent regressions in the future. All jest packages in use
have been updated as part of this commit.

Fixes #129

__tests__/__snapshots__/snapshotDiff.test.js.snap

@@ -166,6 +166,11 @@ exports[`failed optional deps throws with sensible message on missing react-test
 Cannot find module 'non-existent-module-for-testing' from '__tests__/snapshotDiff.test.js'"
 `;
 
+exports[`no difference 1`] = `
+"Snapshot Diff:
+Compared values have no visual difference."
+`;
+
 exports[`shows diff when comparing React fragments of varying length 1`] = `
 "Snapshot Diff:
 - <FragmentComponent />

__tests__/snapshotDiff.test.js

@@ -267,3 +267,7 @@ describe('failed optional deps', () => {
     ).toThrowErrorMatchingSnapshot();
   });
 });
+
+test('no difference', () => {
+  expect(snapshotDiff('a', 'a')).toMatchSnapshot();
+});

package.json

@@ -22,9 +22,9 @@
     "jest": ">=16"
   },
   "dependencies": {
-    "jest-diff": "^26.0.1",
-    "jest-snapshot": "^26.0.1",
-    "pretty-format": "^26.0.1"
+    "jest-diff": "^26.1.0",
+    "jest-snapshot": "^26.1.0",
+    "pretty-format": "^26.1.0"
   },
   "devDependencies": {
     "@babel/cli": "^7.7.0",
@@ -38,7 +38,7 @@
     "enzyme-to-json": "^3.4.0",
     "eslint": "^7.0.0",
     "flow-bin": "^0.127.0",
-    "jest": "^26.0.1",
+    "jest": "^26.1.0",
     "react": "^16.13.1",
     "react-dom": "16.13.1",
     "react-test-renderer": "^16.13.1"