Fix wrong viewBox in the towergit-plain-wordmark.svg file (#792)

[Thomas-Boi]

---

name: Pull Request Template
about: Add a new icon or feature to the repo.
title: 'New Icon/Feature: [NAME]'
assignees: ''

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New Icon Section

Double check these details before you open a PR

• [] PR does not match another non-stale PR currently opened
• [] PR name matches the format new icon: Icon name (versions separated by comma). More details here
• [] PR's base is the develop branch.
• [] Your icons are inside a folder as seen here
• [] SVG matches the standards laid out here
• [] A new object is added in the devicon.json file as seen here

Link to prove your SVG is correct and up-to-date.

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New Feature Section

Double check these details before you open a PR**

• [] PR does not match another non-stale PR currently opened
• [] PR name matches the format New Feature: brief description of feature

This PR adds/fixes...

Notes