renames fixtures as testdata to avoid spurious dependencies (#359)

testdata/max-public-structs.go

@@ -0,0 +1,11 @@
+// Package pkg ...
+package pkg // MATCH /you have exceeded the maximum number of public struct declarations/
+
+type Foo struct {
+}
+
+type Bar struct {
+}
+
+type Baz struct {
+}