Make compression_merge_race test output not depend on chunk name

Author: svenklemm

tsl/test/isolation/expected/compression_merge_race.out

@@ -98,11 +98,11 @@ count|expected
 
 starting permutation: s1_compress_single_chunk s1_compress_all_chunks_single_transaction s3_select_on_compressed_chunk s3_wait_for_finish s1_compress_finish
 step s1_compress_single_chunk: 
-    select compress_chunk(c, true) from show_chunks('sensor_data') c limit 1;
+    select compress_chunk(c, true) is not null as compress from show_chunks('sensor_data') c limit 1;
 
-compress_chunk                             
--------------------------------------------
-_timescaledb_internal._hyper_X_X_chunk
+compress
+--------
+t       
 
 step s1_compress_all_chunks_single_transaction: 
     BEGIN;

tsl/test/isolation/specs/compression_merge_race.spec

@@ -74,7 +74,7 @@ step "s1_compress_finish" {
 }
 
 step "s1_compress_single_chunk" {
-    select compress_chunk(c, true) from show_chunks('sensor_data') c limit 1;
+    select compress_chunk(c, true) is not null as compress from show_chunks('sensor_data') c limit 1;
 }