how to remove visual studio PIN TAB icon (on tabs, obviously)

Scroll to the bottom of the Document Tab Well -> General page, click Advanced options..., then uncheck Show pin button in unpinned tabs

To remove the pin tab icon from Visual Studio 2019, Visual Studio 2017, Visual Studio 2015, Visual Studio 2013 and Visual Studio 2012, there is an option within the Visual Studio Environment settings.

Tools Menu -> Options -> Environment -> Tabs and Windows -> Under the "Pinned Tabs" section, uncheck "Show pin button in unpinned tabs"

The image above is from Visual studio 2019, but is relevant to Visual Studio 2017, 2015, 2013, and 2012 as well.