Labels Filter Bar Static Height, and invisible scroll bar

[seetohjinwei]

Describe the bug

1. For a repository with no labels: it displays a fixed height container
2. For a repository with many issues: the container is scrollable, but there is no visible scroll bar
   • this seems to be intentional based on the CSS, but I feel like this might lead to the user being unaware that the container is scrollable

To Reproduce

1. Visit a repository with no labels, and a repository with many labels.
2. Click on the labels dropdown

Expected behavior

1. For a repository with no labels: the container's height should dynamically decrease
2. For a repository with many issues: the container's scroll bar should be visible

• Change height: 400px to max-height: 400px
• Allow the scrollbar to be visible when there is content to be scrolled

Screenshots

Repository with many labels:

Repository with no labels:

Desktop (please complete the following information):

• OS: macos Ventura
• Browser: Chrome, Firefox

Additional context

Related to #17.