fix: vault logging structure (#2180)

Signed-off-by: Moritz Johner <beller.moritz@googlemail.com>

pkg/provider/vault/vault.go

@@ -1414,7 +1414,7 @@ func init() {
 	// max. 265k vault leases with 30bytes each ~= 7MB
 	fs.IntVar(&vaultTokenCacheSize, "experimental-vault-token-cache-size", 2<<17, "Maximum size of Vault token cache. When more tokens than Only used if --experimental-enable-vault-token-cache is set.")
 	lateInit := func() {
-		logger.Info("initializing vault cache with size=%d", vaultTokenCacheSize)
+		logger.Info("initializing vault cache", "size", vaultTokenCacheSize)
 		clientCache = cache.Must(vaultTokenCacheSize, func(client util.Client) {
 			err := revokeTokenIfValid(context.Background(), client)
 			if err != nil {