Spin boxes in Sample Transmission Calculator allows typing comma

[warunawickramasingha]

In single wavelength, the spin boxes for Low, Width, High in the Sample Transmission Calculator interface allows its spin boxes to enter values such as 0,2.1 to include comma which should not be allowed.

Describe the bug

To Reproduce

1. Follow instructions of Sample Transmission Calculator
2. Try entering numbers with comma in the spin boxes under single wavelength mode for Low/Width/High boxes

Expected behavior
Comma should not be allowed

Platform/Version (please complete the following information):

• OS: [all]
• OS Version:
• Mantid Version 6.11

Additional context