[chore] fix failing syslog load test (open-telemetry#37197)

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#### Description

The loadtest is failing due to missing year in the timestamp. The
timestamp `Oct 11 22:14:15` was until Oct 10 2024 calculated with the
year 2023 (`1697062455000000000`) and since then, it by default takes
the year 2024, so it results in the following timestamp
`1728684855000000000` and causes the test to fail.

Failing run on main:
https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/12757989830/job/35563296082

## Note

failing lint test will be resolved in a separate PR
open-telemetry#37194

Signed-off-by: odubajDT <ondrej.dubaj@dynatrace.com>

testbed/tests/syslog_integration_test.go

@@ -69,7 +69,7 @@ func TestSyslogComplementaryRFC5424(t *testing.T) {
 func TestSyslogComplementaryRFC3164(t *testing.T) {
 	expectedData := []expectedDataType{
 		{
-			message:        "<34>Oct 11 22:14:15 mymachine su: 'su root' failed for lonvick on /dev/pts/8",
+			message:        "<34>Oct 11 2023 22:14:15 mymachine su: 'su root' failed for lonvick on /dev/pts/8",
 			timestamp:      1697062455000000000,
 			severityNumber: 18,
 			severityText:   "crit",
@@ -82,7 +82,7 @@ func TestSyslogComplementaryRFC3164(t *testing.T) {
 			},
 		},
 		{
-			message:        "<19>Oct 11 22:14:15 - -",
+			message:        "<19>Oct 11 2023 22:14:15 - -",
 			timestamp:      1697062455000000000,
 			severityNumber: 17,
 			severityText:   "err",