Make ImageDataProvider in test adhere to linear scaling requirement

[HeikoKlare]

Fixes these logged warnings in test execution, e.g., in https://github.com/eclipse-platform/eclipse.platform.swt/actions/runs/18940122934/job/54076562163?pr=2711:

***WARNING: ImageData should be linearly scaled across zooms but size is (1, 1) at 100% and (1, 1) at 200%.
java.lang.Error
	at org.eclipse.swt.internal.DPIUtil.validateLinearScaling(DPIUtil.java:247)
	at org.eclipse.swt.graphics.Image.lambda$0(Image.java:679)
	at org.eclipse.swt.internal.StrictChecks.runIfStrictChecksEnabled(StrictChecks.java:28)
	at org.eclipse.swt.graphics.Image.<init>(Image.java:678)
	at org.eclipse.swt.tests.junit.Test_org_eclipse_swt_graphics_GC.test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataAtSizeProvider(Test_org_eclipse_swt_graphics_GC.java:498)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)

[github-actions]

Test Results

  118 files  ±0    118 suites  ±0   17m 6s ⏱️ + 1m 58s
4 650 tests ±0  4 633 ✅ ±0  17 💤 ±0  0 ❌ ±0 
  330 runs  ±0    326 ✅ ±0   4 💤 ±0  0 ❌ ±0 

Results for commit da031b6. ± Comparison against base commit 485749a.

[akurtakov]

New compiler warnings are coming from eclipse-jdt/eclipse.jdt.core#4572 . Merging.