Fix clock number position issue

[bndynet]

This PR closes #1321

Description

If overwrite theme spacing as below at https://material-ui.com/customization/spacing/#custom-spacing. The clock number position is not right.

const theme = createMuiTheme({
  spacing: factor => `${0.25 * factor}rem`, // (Bootstrap strategy)
});

Screenshot

[codecov]

Codecov Report

Merging #1327 into next will decrease coverage by 0.14%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##            next    #1327      +/-   ##
=========================================
- Coverage   93.7%   93.56%   -0.15%     
=========================================
  Files         55       55              
  Lines       1350     1351       +1     
  Branches     199      200       +1     
=========================================
- Hits        1265     1264       -1     
- Misses        67       68       +1     
- Partials      18       19       +1

Impacted Files	Coverage Δ
lib/src/views/Clock/ClockNumber.tsx	89.47% <0%> (-4.98%)	⬇️
lib/src/views/Clock/ClockPointer.tsx	92% <0%> (-4%)	⬇️

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