Replace references to COLLATE "en_US" with COLLATE "C".

Commit f0e44751 is turning the
buildfarm red; let's try something hopefully more portable.

src/test/regress/expected/alter_table.out

@@ -3034,7 +3034,7 @@ DROP TABLE unparted, fail_part;
 -- check that partition bound is compatible
 CREATE TABLE list_parted (
 	a int NOT NULL,
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	CONSTRAINT check_a CHECK (a > 0)
 ) PARTITION BY LIST (a);
 CREATE TABLE fail_part (LIKE list_parted);
@@ -3117,7 +3117,7 @@ ERROR:  child table "fail_part" has different collation for column "b"
 DROP TABLE fail_part;
 -- check that the table being attached has all constraints of the parent
 CREATE TABLE fail_part (
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	a int NOT NULL
 );
 ALTER TABLE list_parted ATTACH PARTITION fail_part FOR VALUES IN (1);
@@ -3130,7 +3130,7 @@ DROP TABLE fail_part;
 -- check the attributes and constraints after partition is attached
 CREATE TABLE part_1 (
 	a int NOT NULL,
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	CONSTRAINT check_a CHECK (a > 0)
 );
 ALTER TABLE list_parted ATTACH PARTITION part_1 FOR VALUES IN (1);

src/test/regress/expected/create_table.out

@@ -391,7 +391,7 @@ CREATE TABLE partitioned (
 	b int,
 	c text,
 	d text
-) PARTITION BY RANGE (a oid_ops, plusone(b), c collate "default", d collate "en_US");
+) PARTITION BY RANGE (a oid_ops, plusone(b), c collate "default", d collate "C");
 -- check relkind
 SELECT relkind FROM pg_class WHERE relname = 'partitioned';
  relkind 
@@ -429,7 +429,7 @@ ERROR:  cannot inherit from partitioned table "partitioned2"
  b      | integer |           |          | 
  c      | text    |           | not null | 
  d      | text    |           | not null | 
-Partition key: RANGE (a oid_ops, plusone(b), c, d COLLATE "en_US")
+Partition key: RANGE (a oid_ops, plusone(b), c, d COLLATE "C")
 
 \d partitioned2
             Table "public.partitioned2"

src/test/regress/sql/alter_table.sql

@@ -1923,7 +1923,7 @@ DROP TABLE unparted, fail_part;
 -- check that partition bound is compatible
 CREATE TABLE list_parted (
 	a int NOT NULL,
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	CONSTRAINT check_a CHECK (a > 0)
 ) PARTITION BY LIST (a);
 CREATE TABLE fail_part (LIKE list_parted);
@@ -1999,7 +1999,7 @@ DROP TABLE fail_part;
 
 -- check that the table being attached has all constraints of the parent
 CREATE TABLE fail_part (
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	a int NOT NULL
 );
 ALTER TABLE list_parted ATTACH PARTITION fail_part FOR VALUES IN (1);
@@ -2012,7 +2012,7 @@ DROP TABLE fail_part;
 -- check the attributes and constraints after partition is attached
 CREATE TABLE part_1 (
 	a int NOT NULL,
-	b char(2) COLLATE "en_US",
+	b char(2) COLLATE "C",
 	CONSTRAINT check_a CHECK (a > 0)
 );
 ALTER TABLE list_parted ATTACH PARTITION part_1 FOR VALUES IN (1);

src/test/regress/sql/create_table.sql

@@ -397,7 +397,7 @@ CREATE TABLE partitioned (
 	b int,
 	c text,
 	d text
-) PARTITION BY RANGE (a oid_ops, plusone(b), c collate "default", d collate "en_US");
+) PARTITION BY RANGE (a oid_ops, plusone(b), c collate "default", d collate "C");
 
 -- check relkind
 SELECT relkind FROM pg_class WHERE relname = 'partitioned';