Token instance image display imrovement

[vbaranov]

Resolves #4935

Motivation

Eliminate error of kind:

Request: GET /token/0x906d56d114ef1bb430a1c450dc6b24df22d3e759/instance/22/token-transfers
** (exit) an exception was raised:
    ** (FunctionClauseError) no function clause matching in URI.encode/2
        (elixir 1.12.2) lib/uri.ex:366: URI.encode(["https://5cryptos.com/wp-content/uploads/2021/06/Shiba-Inu-Grain-NFT-004.png"], #Function<1.66049009/1 in URI."-fun.char_unescaped?/1-">)
        (block_scout_web 0.0.1) lib/block_scout_web/views/tokens/instance/overview_view.ex:159: BlockScoutWeb.Tokens.Instance.OverviewView.retrieve_image/2
        (block_scout_web 0.0.1) lib/block_scout_web/views/tokens/instance/overview_view.ex:34: BlockScoutWeb.Tokens.Instance.OverviewView.media_src/1
        (block_scout_web 0.0.1) lib/block_scout_web/templates/tokens/instance/overview/_details.html.eex:65: BlockScoutWeb.Tokens.Instance.OverviewView."_details.html"/1
        (block_scout_web 0.0.1) lib/block_scout_web/templates/tokens/instance/transfer/index.html.eex:2: BlockScoutWeb.Tokens.Instance.TransferView."index.html"/1
        (phoenix 1.5.13) lib/phoenix/view.ex:310: Phoenix.View.render_within/3
        (phoenix 1.5.13) lib/phoenix/view.ex:472: Phoenix.View.render_to_iodata/3
        (phoenix 1.5.13) lib/phoenix/controller.ex:777: Phoenix.Controller.render_and_send/4

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools