Change version-sensitive tests to handle '10'

Previously assumed period in version; this makes tests future-proof.

src/test/regress/expected/multi_explain.out

@@ -3,7 +3,7 @@
 --
 ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 570000;
 -- print major version to make version-specific tests clear
-SELECT substring(version(), '\d+\.\d+') AS major_version;
+SELECT substring(version(), '\d+(?:\.\d+)?') AS major_version;
  major_version 
 ---------------
  9.6

src/test/regress/expected/multi_explain_0.out

@@ -3,7 +3,7 @@
 --
 ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 570000;
 -- print major version to make version-specific tests clear
-SELECT substring(version(), '\d+\.\d+') AS major_version;
+SELECT substring(version(), '\d+(?:\.\d+)?') AS major_version;
  major_version 
 ---------------
  9.5

src/test/regress/input/multi_subquery.source

@@ -7,7 +7,7 @@ ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 270000;
 
 -- print major version to make version-specific tests clear
 SHOW server_version \gset
-SELECT substring(:'server_version', '\d+\.\d+') AS major_version;
+SELECT substring(:'server_version', '\d+(?:\.\d+)?') AS major_version;
 
 
 -- Create tables for subquery tests

src/test/regress/output/multi_subquery.source

@@ -4,7 +4,7 @@
 ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 270000;
 -- print major version to make version-specific tests clear
 SHOW server_version \gset
-SELECT substring(:'server_version', '\d+\.\d+') AS major_version;
+SELECT substring(:'server_version', '\d+(?:\.\d+)?') AS major_version;
  major_version 
 ---------------
  9.6

src/test/regress/output/multi_subquery_0.source

@@ -4,7 +4,7 @@
 ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 270000;
 -- print major version to make version-specific tests clear
 SHOW server_version \gset
-SELECT substring(:'server_version', '\d+\.\d+') AS major_version;
+SELECT substring(:'server_version', '\d+(?:\.\d+)?') AS major_version;
  major_version 
 ---------------
  9.5

src/test/regress/sql/multi_explain.sql

@@ -5,7 +5,7 @@
 ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 570000;
 
 -- print major version to make version-specific tests clear
-SELECT substring(version(), '\d+\.\d+') AS major_version;
+SELECT substring(version(), '\d+(?:\.\d+)?') AS major_version;
 
 \a\t