chore: add `flash-attention` to docker ignore (#287)

included when building docker locally.
(Where the local dirs might have the flash-attention folder.)


# What does this PR do?

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Fixes # (issue)


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.dockerignore

@@ -1,3 +1,4 @@
 aml
 target
-server/transformers
+server/transformers
+server/flash-attention