Fix some images linked to GitHub

Clicking the image make jump to GitHub page, but this is just annoying,
and this seems to make the sizes of the images smaller.

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Author: daipom

buffer/README.md

@@ -30,7 +30,7 @@ You can think of a chunk as a cargo box. A buffer plugin uses a chunk as a light
 
 Internally, a buffer plugin has two separated places to store its chunks: _"stage"_ where chunks get filled with events, and _"queue"_ where chunks wait before the transportation. Every newly-created chunk starts from _stage_, then proceeds to _queue_ in time \(and subsequently gets transferred to the destination\).
 
-[![Fluentd-v0.14 Plugin API Overview](../.gitbook/assets/fluentd-v0.14-plugin-api-overview.png)](https://github.com/fluent/fluentd-docs-gitbook/tree/da81ba70252eaa863cc28fc888584c59d6fc14d3/images/fluentd-v0.14-plugin-api-overview.png)
+![Fluentd-v0.14 Plugin API Overview](../.gitbook/assets/fluentd-v0.14-plugin-api-overview.png)
 
 ## Control Retry Behavior
 

installation/install-by-msi.md

@@ -164,7 +164,7 @@ It's working properly if td-agent process outputs:
 test.event: {"k", "v"}
 ```
 
-[![Td-agent Windows Prompt](../.gitbook/assets/td-agent-windows-prompt.png)](https://github.com/fluent/fluentd-docs-gitbook/tree/da81ba70252eaa863cc28fc888584c59d6fc14d3/images/td-agent-windows-prompt.png)
+![Td-agent Windows Prompt](../.gitbook/assets/td-agent-windows-prompt.png)
 
 ### Step 3: Register `td-agent` to Windows Service