abi: fix abigen issue with make devtools (#10091)

fixes #7593 

it introduced a regression: `"fmt"` and `"reflect"` imports were added
for all files generated by `abigen` assuming that they will be used in
all cases, however that assumption was wrong for some cases resulting in
invalid code being generated (in this case after running `make
devtools`):
<img width="982" alt="Screenshot 2024-04-27 at 10 50 37"
src="https://github.com/ledgerwatch/erigon/assets/94537774/9a1b93a5-2141-40d9-8c9e-01a1ff6c031c">

accounts/abi/bind/template.go

@@ -90,8 +90,21 @@ package {{.Package}}
 import (
 	"math/big"
 	"strings"
-	"fmt"
-	"reflect"
+
+{{range .Contracts}}
+	{{$stop := false}}
+	{{range .Transacts}}
+		{{if ne (len .Normalized.Inputs) 0}}
+			"fmt"
+			"reflect"
+			{{$stop = true}}
+			{{break}}
+		{{end}}
+	{{end}}
+	{{if $stop}}
+		{{break}}
+	{{end}}
+{{end}}
 
 	ethereum "github.com/ledgerwatch/erigon"
 	"github.com/ledgerwatch/erigon/accounts/abi"