event: remove unused code

The variable v was introduced for the EventMetric case with
CL 682695 but never used.

Change-Id: I5754b0ec6769b23829dcf71d34b6b68bca2baeed
Reviewed-on: https://go-review.googlesource.com/c/exp/+/745640
Auto-Submit: Sean Liao <sean@liao.dev>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>

trace/event.go

diff --git a/trace/event.go b/trace/event.go
index 52bd564..5cced18 100644
--- a/trace/event.go
+++ b/trace/event.go
@@ -16,7 +16,6 @@
 	"math"
 	"regexp"
 	"slices"
-	"strconv"
 	"strings"
 	"time"
 
@@ -1272,10 +1271,6 @@
 	switch kind := e.Kind(); kind {
 	case EventMetric:
 		m := e.Metric()
-		v := m.Value.String()
-		if m.Value.Kind() == ValueString {
-			v = strconv.Quote(v)
-		}
 		fmt.Fprintf(&sb, " Name=%q Value=%s", m.Name, m.Value)
 	case EventLabel:
 		l := e.Label()