Pick up only those tags starting with a 'v' (FairwindsOps#2)

The list-all command is picking up an accidental tag which doesn't have the `v` prefix.

```sh
❯ bin/list-all | | grep "5\.10\.1"
5.10.1
"5.10.1.z'
```

This breaks the latest-all command

```sh
❯ asdf latest --all | grep pluto
pluto	"5.10.1.z	missing
```

Co-authored-by: Andrew Suderman <andy@suderman.dev>

bin/list-all

@@ -12,5 +12,5 @@ function sort_versions() {
     LC_ALL=C sort -t. -k 1,1 -k 2,2n -k 3,3n -k 4,4n -k 5,5n | awk '{print $2}'
 }
 
-versions=$(eval $cmd | grep -oE "tag_name\": *\".{1,15}\"," | sed 's/tag_name\": *\"v//;s/\",//' | sort_versions)
+versions=$(eval $cmd | grep -oE "tag_name\": *\"v.*.{1,15}\"," | sed 's/tag_name\": *\"v//;s/\",//' | sort_versions)
 echo $versions