[MINOR] Remove duplicate entry in .gitignore

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Closes apache#4837 from MyLanPangzi/patch-2.

Signed-off-by: Cheng Pan <[email protected]>

.gitignore

@@ -34,7 +34,6 @@ conf/keystore
 conf/truststore
 conf/interpreter.json
 conf/notebook-authorization.json
-conf/shiro.ini
 conf/credentials.json
 conf/helium.json