Whitespace at the beginning or end of the recovery key prevents wallet recovery

[btlechowski]

Steps to Reproduce

1. Go to brave://rewards/
2. In Manage You Wallet use a recovery key with whitespace at the end/beginning of the key (tried Space and Enter)
3. Restore the wallet

Actual result:

User may get the wrong impression that wallet recovery does not work even though recovery key is correct.

Expected result:

Whitespace is trimmed from the beginning and the end of the recovery key

Reproduces how often:

always

Brave version (brave://version info)

Brave	0.58.16 Chromium: 71.0.3578.98 (Official Build) (64-bit)
Revision	15234034d19b85dcd9a03b164ae89d04145d8368-refs/branch-heads/3578@{#897}
OS	Windows 7

cc @NejcZdovc @brave/legacy_qa

[LaurenWags]

Verified passed with

Brave	0.60.23 Chromium: 72.0.3626.96 (Official Build) beta(64-bit)
Revision	84098ee7ef8622a9defc2ef043cd8930b617b10e-refs/branch-heads/3626@{#836}
OS	Mac OS X

• Verified test plan from Fixes whitespace when doing restore brave-core#1169

Verification PASSED on Mint 19.1 x64 using the following build:

Brave	0.60.26 Chromium: 72.0.3626.96 (Official Build) beta(64-bit)
Revision	84098ee7ef8622a9defc2ef043cd8930b617b10e-refs/branch-heads/3626@{#836}
OS	Linux

Verification passed on

Brave	0.60.27 Chromium: 72.0.3626.96 (Official Build) beta (64-bit)
Revision	84098ee7ef8622a9defc2ef043cd8930b617b10e-refs/branch-heads/3626@{#836}
OS	Windows 10

• Verified test plan from Fixes whitespace when doing restore brave-core#1169