Reduce machine size to 512MB

With current cover caching headers, the number of requests per page is
generally lower (except for one single spike when image cache expires).
It's therefore acceptable to lower the amount of connections in the
pool, which in turn decreases the amount of needed memory.

fly.toml

@@ -14,7 +14,7 @@ DATABASE_PATH = '/mnt/music_library/music_library_prod.db'
 PHX_HOST = 'music-library.claudio-ortolina.org'
 PORT = '8080'
 LAST_FM_USER = 'cloud8421'
-POOL_SIZE = '20'
+POOL_SIZE = '10'
 
 [[mounts]]
 source = 'music_library'
@@ -34,6 +34,6 @@ hard_limit = 1000
 soft_limit = 1000
 
 [[vm]]
-memory = '1024mb'
+memory = '512mb'
 cpu_kind = 'shared'
 cpus = 1