add_compression_policy migration helper raises a syntax error

[AaronCDee]

Hi there,

There is a syntax error in the add_compression_policy migration helper when including thecompression_chunk_time_interval argument.

The issue is that it uses the following syntax:

"timescaledb.compression_chunk_time_interval = INTERVAL '#{compression_chunk_time_interval}'"

The TigerData docs specify that there should be no INTERVAL keyword used and should just be set to the given interval eg:

ALTER TABLE <table_name> SET (
   timescaledb.compress,
   timescaledb.compress_orderby = '<column_name> [ASC | DESC] [ NULLS { FIRST | LAST } ] [, ...]',
   timescaledb.compress_segmentby = '<column_name> [, ...]',
   timescaledb.compress_chunk_time_interval='interval' # No INTERVAL key word used here
);

I can open a PR to fix this error, as we needed this and weren't able to use it because of the error.