Set test config to the value it was designed with

The tests here were set using the old default of 300 for pixelMargin
(now updated to 250).  Rather than change the tests, override the
config in the test to the value it was conditioned on.

tests/test_loadDiaCatalogs.py

@@ -370,6 +370,7 @@ def testGetPixelRanges(self):
         the WCS.
         """
         diaConfig = LoadDiaCatalogsConfig()
+        diaConfig.pixelMargin = 300  # overriding to value tests were conditioned on
         diaConfig.htmMaxRanges = 4
         diaLoader = LoadDiaCatalogsTask(config=diaConfig)