content: Inline code links should be rendered with the link color

[PIG208]

We should fix inline code's color when it is a part of a link.

web (expected)	flutter

Since a recent change (https://github.com/zulip/zulip-flutter/commit/299c76be7), inline code links no longer have the ambient color and is always black. We want to fix this to match the behavior of the web app.

For reference, the web app defines a separate CSS variable --color-markdown-code-link

    --color-markdown-link: hsl(200deg 100% 40%);
    --color-markdown-code-link: var(--color-markdown-link);

that applies to inline code that appears inside a link:

    & a {
        color: var(--color-markdown-link);
        text-decoration: none;

        & code {
            color: var(--color-markdown-code-link);
        }