test(stock): drop non numeric reading from formula based quality inspection

a numeric reading of "random text" was read as 0 and pulled the mean from
0.6 down to 0.4, which the test then asserted as accepted. such a reading
is now rejected outright, and the test is about formula evaluation, so drop
the row. its assertions are unchanged.

(cherry picked from commit 3752be809f)

erpnext/stock/doctype/quality_inspection/test_quality_inspection.py

@@ -108,7 +108,6 @@ class TestQualityInspection(ERPNextTestSuite):
 				"acceptance_formula": "mean < 0.9",
 				"reading_1": "0.5",
 				"reading_2": "0.7",
-				"reading_3": "random text",  # check if random string input causes issues
 			},
 			{
 				"specification": "Calcium Content",  # non-numeric reading