Update mutual-ssl-between-api-gateway-and-backend.md

[charithjayasanka]

Removed an unnecessary newline character that was causing a FileNotFoundException when customers directly used and copied the configuration path. This improvement aims to prevent potential confusion, particularly for customers encountering this issue.

Details
Previously, an extra newline in the path caused the following exception when users attempted to load the client truststore file directly:

java.io.FileNotFoundException: repository/resources/security/client-truststore.jks
     (No such file or directory)

This update ensures the path is correctly formatted to avoid such exceptions, streamlining the setup process and improving usability for end-users.

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