Ignore pg_dynshmem fiel when comparing directories (#9374)

## Problem

At MacOS `pg_dynshmem` file is create in PGDATADIR which cause mismatch
in directories comparison

## Summary of changes

Add this files to the ignore list.

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>

test_runner/fixtures/neon_fixtures.py

@@ -4280,6 +4280,7 @@ SKIP_FILES = frozenset(
         "postmaster.opts",
         "postmaster.pid",
         "pg_control",
+        "pg_dynshmem",
     )
 )