fmp_13f years not being processed correctly

I believe that there is a problem with the `fmp_13f` function. When I run the following lines of code:

```
berkshire_cik <- '0001067983'
form_13FStatement_2020 <- fmp_13f(cik = berkshire_cik, year = 2020)
form_13FStatement_2019 <- fmp_13f(cik = berkshire_cik, year = 2019)
```

I get the exact same result. That is, not collecting previous years data - only collecting 2021 data.