Update pg_query to v2.1.1

We disabled GC due in pg_query to work around
https://github.com/pganalyze/pg_query/issues/226, but this turned out to
be a bug where the Ruby garbage collector might incorrectly garbage
collect an intermediate variable
(https://bugs.ruby-lang.org/issues/18140#note-2).

https://github.com/pganalyze/pg_query/pull/227 works around the problem
by calling to_ary to ensure the Ruby interpreter does not do this. As a
result, we can remove the workaround.

Gemfile.lock

@@ -907,7 +907,7 @@ GEM
     peek (1.1.0)
       railties (>= 4.0.0)
     pg (1.2.3)
-    pg_query (2.1.0)
+    pg_query (2.1.1)
       google-protobuf (>= 3.17.1)
     plist (3.6.0)
     png_quantizator (0.2.1)

spec/support/database/prevent_cross_database_modification.rb

@@ -81,15 +81,8 @@ module Database
 
       # PgQuery might fail in some cases due to limited nesting:
       # https://github.com/pganalyze/pg_query/issues/209
-      #
-      # Also, we disable GC while parsing because of https://github.com/pganalyze/pg_query/issues/226
-      begin
-        GC.disable
       parsed_query = PgQuery.parse(sql)
       tables = sql.downcase.include?(' for update') ? parsed_query.tables : parsed_query.dml_tables
-      ensure
-        GC.enable
-      end
 
       return if tables.empty?
 

spec/support/database/prevent_cross_joins.rb

@@ -33,14 +33,7 @@ module Database
 
       # PgQuery might fail in some cases due to limited nesting:
       # https://github.com/pganalyze/pg_query/issues/209
-      #
-      # Also, we disable GC while parsing because of https://github.com/pganalyze/pg_query/issues/226
-      begin
-        GC.disable
       tables = PgQuery.parse(sql).tables
-      ensure
-        GC.enable
-      end
 
       schemas = Database::GitlabSchema.table_schemas(tables)