all: clean up lint identified by ruleguard

Ruleguard run with ruleguard -c=0 -rules ruleguard.rules.go ./... from
https://github.com/dgryski/semgrep-go with the following rules inactivated
to reduce noise:

- unconvert for floating point values
- oddcomparisons
- floateq

graph/encoding/graphql/decode_test.go

@@ -175,7 +175,7 @@ type node struct {
 }
 
 func (n *node) ID() int64     { return int64(n.id) }
-func (n *node) DOTID() string { return fmt.Sprintf("0x%016x", uint64(n.id)) }
+func (n *node) DOTID() string { return fmt.Sprintf("0x%016x", n.id) }
 
 func (n *node) SetIDFromString(uid string) error {
 	if !strings.HasPrefix(uid, "0x") {