GAP.jl 0.7.4 released

Today GAP.jl 0.7.4 has been released.

Diff since v0.7.3

Closed issues:

• Silence banner of GAP.jl when loaded from another package (#765)

Merged pull requests:

• Better banner suppression logic (#768) (@fingolfin)
• Rewrite anon function arg for atexit as a do-block (#769) (@fingolfin)
• CI: switch to codecov/codecov-action@v2 (#770) (@fingolfin)