test(chartutil): Update error message in schema validation test

- Refine expected error message for the `TestValidateAgainstSchemaNegative` test
- Provides clearer feedback by specifying an incomplete integer value error instead of a generic missing field error

Signed-off-by: Jiří Altman <jiri.altman@usu.com>

pkg/chartutil/jsonschema_test.go

@@ -159,7 +159,7 @@ func TestValidateAgainstSchemaNegative(t *testing.T) {
 	}
 
 	expectedErrString := `subchart:
-- (root): age is required
+age: incomplete value >=0 & int
 `
 	if errString != expectedErrString {
 		t.Errorf("Error string :\n`%s`\ndoes not match expected\n`%s`", errString, expectedErrString)