Fix broken tags in two configuration examples (#707)

- syslog-influxdb: close <buffer> with </buffer>. The example failed
  with "unmatched end tag" and Fluentd did not start.
- rewrite_tag_filter: drop the stray ">" from the deparser tag. The
  events never reached the <match irc.http_5xx_error> section.

Signed-off-by: Shizuo Fujita <fujita@clear-code.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: Watson1978

how-to-guides/syslog-influxdb.md

@@ -86,7 +86,7 @@ Finally, configure `/etc/fluent/fluentd.conf` as follows:
   use_ssl false
   <buffer>
     flush_interval 10s # for testing
-  <buffer>
+  </buffer>
 </match>
 ```
 

output/rewrite_tag_filter.md

@@ -447,7 +447,7 @@ The plugins are required to be installed:
 # sample results: {"message":"HTTP Status warn [5xx_count] apache.access: 1.0 (threshold 1.0)"}
 <match alert.http_5xx_error>
   @type deparser
-  tag irc.http_5xx_error>
+  tag irc.http_5xx_error
   format_key_names level,target_key,target_tag,value,threshold
   format HTTP Status %s [%s] %s: %s (threshold %s)
   key_name message