config: Increase transform logs buffer cap

prev: 100_KiB
new:  500_KiB

Integration tests have started failing due to the buffer being full.

Signed-off-by: Oren Leiman <oren.leiman@redpanda.com>

src/v/config/configuration.cc

@@ -226,7 +226,7 @@ configuration::configuration()
       "calculated as the total size of buffered (i.e. emitted but not yet "
       "produced) log messages.",
       {.needs_restart = needs_restart::yes, .visibility = visibility::tunable},
-      100_KiB,
+      500_KiB,
       {.min = 100_KiB, .max = 2_MiB})
   , data_transforms_logging_flush_interval_ms(
       *this,