entered gateway address not retained in "Set IPFS gateway" modal

[LaurenWags]

Description

Found while testing #11563

When the "IPFS public gateway address" setting is modified in brave://settings/extensions, it shows on the settings page. However, if you click the Change button again, your updated URL is not shown in the Set IPFS gateway box, the default URL is shown

Steps to Reproduce

1. Open brave://settings/extensions
2. Click the Change button for "IPFS public gateway address"
3. Enter a different gateway (ex. https://cf-ipfs.com)
4. Click Submit.
5. See updated URL on settings page.
6. Click Change button again.

Actual result:

Default URL is shown, not what you entered:

Expected result:

I expected the gateway URL I entered to be shown on the Set IPFS gateway popup.

Reproduces how often:

easily

Brave version (brave://version info)

Brave | 1.20.88 Chromium: 88.0.4324.96 (Official Build) dev (x86_64)
-- | --
Revision | 68dba2d8a0b149a1d3afac56fa74648032bcf46b-refs/branch-heads/4324@{#1784}
OS | macOS Version 10.15.7 (Build 19H15)

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a 1.19.x
• Can you reproduce this issue with the beta channel? yes 1.20.x
• Can you reproduce this issue with the nightly channel? yes 1.21.x

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

cc @bbondy @yrliou

[stephendonner]

Verified FIXED using nightly build with the inline steps to reproduce

Brave	1.23.39 Chromium: 89.0.4389.90 (Official Build) nightly (x86_64)
Revision	62eb262cdaae9ef819aadd778193781455ec7a49-refs/branch-heads/4389@{#1534}

Steps:

1. Opened brave://settings/extensions
2. Click the Change button for "IPFS public gateway address"
3. Entered a different gateway (https://cf-ipfs.com)
4. Clicked Submit
5. Saw updated URL on settings page.
6. Clicked Change button again.

Verified that after clicking on the Change button again in step 6, the URL (https://cf-ipfs.com) I entered in step 3 persisted.