pgsql: Fix pg_walsummary's .gitignore

Fix pg_walsummary's .gitignore

It missed a entry for tmp_check/ generated by the tests. While on it,
append a slash at the beginning of "pg_walsummary" to restrict its check
to the current directory, like anywhere else.

Oversights in ee1bfd168390.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/278972f5933679e06e7d71d2060c1867f5aa4ebe

Modified Files
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src/bin/pg_walsummary/.gitignore | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)