[CI] Fix wrong extension for the configuration file in the build bot
[CI] Fix wrong extension for the configuration file in the build bot

Summary: A bad typo occured in D7357...

Test Plan: Check the diff build is alive again after this diff lands.

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7373

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