Fix extra character in countdown

[MandipGiri]

• Fix extra character getting printed while countdown was running.
• Should fix https://github.com/samit22/calendarN/issues/16

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
cmd/countdown.go	83.82% <60.00%> (-2.34%)	:arrow_down:

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