gdb: remove unused includes from dwarf2/index-write.c

These includes are reported as unused by clangd.

Change-Id: Ibf3cdc881abad5f5969edca623412ceac7212149

gdb/dwarf2/index-write.c

diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
index 70688d7..e82d38a 100644
--- a/gdb/dwarf2/index-write.c
+++ b/gdb/dwarf2/index-write.c
@@ -38,12 +38,10 @@
 #include "objfiles.h"
 #include "ada-lang.h"
 #include "dwarf2/tag.h"
-#include "gdbsupport/gdb_tilde_expand.h"
 #include "dwarf2/read-debug-names.h"
 #include "extract-store-integer.h"
 
 #include <algorithm>
-#include <cmath>
 #include <map>
 #include <unordered_map>
 #include <unordered_set>