CHORE: replace "Toolpad" default title with empty string

[Petar-Dimitrov-AXA]

As discussed in issue #4445, I replaced the default "Toolpad" title with an empty string.

[Janpot]

You should be able to set it to empty string on the user side. I think I'm in favor of keeping a default of "Toolpad", because it makes this option more discoverable.

[Petar-Dimitrov-AXA]

If that's the case, please consider adding a disableHeaderTitle prop. Setting the title to '' from client side feels kind a pointless. It would be ideal if there's a disableHeaderTitle boolean prop so that the title node will not render.

[Janpot]

To add more options, perhaps a bit more versatile is to have a prop on the DashboardLayout to override the title? Set it to any value you want to override the branding context, or empty string to disable altogether.