Fix incorrect use of 'exclamation mark'

[daobrien]

https://stylepedia.net/style/6.2/#s

This entry uses "exclamation mark" but everywhere else uses "exclamation point".

shebang
n. Refers to the character sequence consisting of the number sign and exclamation mark (#!) at the beginning of a script. Do not use hashbang or pound-bang or other variations.