How do you remove or change the "Welcome to the Frontpage" title?

From Joomla! Documentation

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The setting for the Page Title is located in the parameters of each Menu Item under "Parameters (System)".

For Example to change the Page Title for the Home page of the Sample web site, (Welcome to the Front Page) you would navigate to
Menus / Main Menu, click on "Home" to open the Menu Item:[Edit] screen.
Then click on "Parameters (System)" to show the System Parameters,
and either change the "Page Title" parameter or set "Show Page Title" to "No".