[SIL.WIndows.Forms] In CustomDropDown, fixed timer check

[imnasnainaec]

If you start with double 0 and add .1 ten times, you can end up with (e.g.) 0.9999999999999999 instead of 1f.

This fixes https://github.com/sillsdev/libpalaso/security/code-scanning/2627

Of the other 14 warnings for "Equality check on floating point values" (https://github.com/sillsdev/libpalaso/security/code-scanning?query=is%3Aopen+branch%3Amaster+rule%3Acs%2Fequality-on-floats), three involve screen DPI (2624, 2625, 2626), and the rest involve font size.

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This change is 

[github-actions]

Palaso Tests

     4 files  ±0       4 suites  ±0   11m 11s ⏱️ +56s
 4 978 tests ±0   4 743 ✅  - 1  235 💤 +1  0 ❌ ±0 
16 186 runs  ±0  15 481 ✅  - 2  705 💤 +2  0 ❌ ±0 

Results for commit d9cc485. ± Comparison against base commit 23dc405.

This pull request skips 1 test.

SIL.Tests.IO.FileLocationUtilitiesTests ‑ LocateInProgramFiles_SendValidProgramDeepSearch_SubFolderSpecified_ReturnsProgramPath

♻️ This comment has been updated with latest results.

[tombogle]

Reviewed 1 of 2 files at r2, all commit messages.
Reviewable status: 1 of 2 files reviewed, 1 unresolved discussion (waiting on @imnasnainaec)

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SIL.Windows.Forms/Widgets/CustomDropDown.cs line 187 at r2 (raw file):

			{
				Opacity += 0.1;
				if (Opacity > .99)

Should we also actually force opacity to be 1f? In practice, I imagine it won't make a noticeable difference (maybe not any difference), so maybe this is just me feeling angst over the imprecision.

To fix the problem, we will add braces {} around the body of the if statement on line 187. This ensures that the scope of the if statement is explicit and matches the indentation. The braces will clarify that Opacity = 1f; is conditionally executed, while timer.Stop(); is always executed after the if statement. No additional imports, methods, or definitions are required for this fix.

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