assert.CollectT: add Helper() method

Add Helper() method to CollectT like testing.T as we intend to add
Helper() to the assert.TestingT interface.

assert/assertions.go

@@ -1874,6 +1874,9 @@ type CollectT struct {
 	errors []error
 }
 
+// Helper is like [testing.T.Helper] but does nothing.
+func (CollectT) Helper() {}
+
 // Errorf collects the error.
 func (c *CollectT) Errorf(format string, args ...interface{}) {
 	c.errors = append(c.errors, fmt.Errorf(format, args...))