Revert previous change to make \centerdot like \cdot
Revert previous change to make \centerdot like \cdot

Summary:
Alpert alerted me to the fact that \centerdot and \cdot are
not the same despite what MathJax thinks.

Test Plan:
- make serve
- load http://localhost:7936/
- see the `a \centerdot b` produces a small, bottom-aligned square

Auditors: alpert emily

kwangkim/katex-npm-0.7.0-pre,azotova/KaTeX,kevinbarabash/KaTeX,kevinbarabash/KaTeX,xymostech/KaTeX,saschatimme/KaTeX,saschatimme/KaTeX,kwangkim/KaTeX,kwangkim/KaTeX,kwangkim/katex-npm-0.7.0-pre,kwangkim/katex-npm-0.7.0-pre,kevinbarabash/KaTeX,kwangkim/KaTeX,kwangkim/katex-npm-0.7.0-pre,xymostech/KaTeX,Khan/KaTeX,kwangkim/katex-npm-0.7.0-pre,kwangkim/KaTeX,Khan/KaTeX,azotova/KaTeX,saschatimme/KaTeX,azotova/KaTeX,xymostech/KaTeX,azotova/KaTeX,xymostech/KaTeX,saschatimme/KaTeX,azotova/KaTeX,kwangkim/KaTeX,xymostech/KaTeX,kevinbarabash/KaTeX,saschatimme/KaTeX,kevinbarabash/KaTeX,Khan/KaTeX