[MV3] Fix e2e encrypt-decrypt test for MV3 test build

[seaona]

Explanation

On the mv3 test build, the e2e test for encrypt-decrypt is failing due to a tiny delay when we render the decrypted text inside MetaMask popup.
This fixes the issue by grabbing the element by its content. This way we make sure the element is there when we make the assertion.

Note: in MV2 this error does not surface as it's slightly faster on rendering the decrypted message. Though tiny delay is not visible on the naked eye, we'll introduce performance metrics for calculating these delays introduced on the MV3 build.

More Information

• Fixes [Bug]: [MV3] e2e failure for Encrypt Decrypt spec #16210
• Relates to https://github.com/MetaMask/metamask-extension/compare/e2e-mv3-incremental?expand=1

Screenshots/Screencaps

Before

After

Manual Testing Steps

1. Build the mv3 test yarn build:test:mv3
2. Run the failing test and check it's working yarn test:e2e:single test/e2e/tests/encrypt-decrypt.spec.js --browser=chrome

Pre-Merge Checklist

• PR template is filled out
• IF this PR fixes a bug, a test that would have caught the bug has been added
• PR is linked to the appropriate GitHub issue
• PR has been added to the appropriate release Milestone

+ If there are functional changes:

• Manual testing complete & passed
• "Extension QA Board" label has been applied

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [bd13506]

• builds: chrome, firefox, opera
• builds (beta): chrome, firefox, opera
• builds (flask): chrome, firefox, opera
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • inpage: inpage
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (2268 ± 100 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	91	259	121	36	17
		domContentLoaded	1888	2636	2254	216	104
		load	1888	2636	2268	209	100
		domInteractive	1888	2636	2254	216	104

[Gudahtt]

LGTM!