[ELF] - Remove dead declaration. NFC.

MipsGotSection::FileGot::isOverflow()
was a dead declararion.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@344342 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/ELF/SyntheticSections.h b/ELF/SyntheticSections.h
index 51a0441..ad3071d 100644
--- a/ELF/SyntheticSections.h
+++ b/ELF/SyntheticSections.h
@@ -340,8 +340,6 @@
     size_t getPageEntriesNum() const;
     // Number of entries require 16-bit index to access.
     size_t getIndexedEntriesNum() const;
-
-    bool isOverflow() const;
   };
 
   // Container of GOT created for each input file.