Kind of a dirty trick, but:
You can set fig.cap=""
on the chunk in question:
Test test test
```{r}
summary(cars)
```
You can also embed plots, for example:
```{r fig.width=7, fig.height=6, fig.cap=""}
plot(cars)
```
Or, you can set fig.cap=""
for all chunks at once in an initializing chunk at the beginning of your Rmd document:
Test test test
```{r options-chunk}
opts_chunk$set(fig.cap="")
```
```{r}
summary(cars)
```
You can also embed plots, for example:
```{r fig.width=7, fig.height=6}
plot(cars)
```