Doc build fix: remove tab from filelist.sgml.

Author: Amit Kapila
Discussion: https://postgr.es/m/CAA4eK1K6z=gu-jppU1dtsyr2BC-pzrq3TYe=RfY+w386dfdiFA@mail.gmail.com

Author: jeff-davis

doc/src/sgml/filelist.sgml

@@ -148,7 +148,7 @@
 <!ENTITY pgsurgery       SYSTEM "pgsurgery.sgml">
 <!ENTITY pgtrgm          SYSTEM "pgtrgm.sgml">
 <!ENTITY pgvisibility    SYSTEM "pgvisibility.sgml">
-<!ENTITY pgwalinspect 	 SYSTEM "pgwalinspect.sgml">
+<!ENTITY pgwalinspect    SYSTEM "pgwalinspect.sgml">
 <!ENTITY postgres-fdw    SYSTEM "postgres-fdw.sgml">
 <!ENTITY seg             SYSTEM "seg.sgml">
 <!ENTITY contrib-spi     SYSTEM "contrib-spi.sgml">