Fix an error in main.mk causing testfixture to use individual fts5 source code files instead of fts5.c.

FossilOrigin-Name: 933a1c818c1d1ccec8680e1ba87f2cbe37cc9f7d
diff --git a/main.mk b/main.mk
index 1e79141..9111b1a 100644
--- a/main.mk
+++ b/main.mk
@@ -388,8 +388,7 @@
   $(TOP)/ext/fts3/fts3_write.c \
   $(TOP)/ext/async/sqlite3async.c \
   $(TOP)/ext/session/sqlite3session.c \
-  $(TOP)/ext/session/test_session.c \
-  $(FTS5_SRC)
+  $(TOP)/ext/session/test_session.c 
 
 # Header files used by all library source files.
 #