[Bitcode] Fix -Wunused-but-set-variable in BitcodeReader.cpp (NFC)

/llvm-project/llvm/lib/Bitcode/Reader/BitcodeReader.cpp:7795:16:
error: variable 'EntryCount' set but not used [-Werror,-Wunused-but-set-variable]
      uint64_t EntryCount = 0;
               ^
1 error generated.

Author: DamonFool

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -7792,7 +7792,6 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
       uint64_t RawFlags = Record[2];
       unsigned InstCount = Record[3];
       uint64_t RawFunFlags = 0;
-      uint64_t EntryCount = 0;
       unsigned NumRefs = Record[4];
       unsigned NumRORefs = 0, NumWORefs = 0;
       int RefListStartIndex = 5;
@@ -7806,7 +7805,6 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
           RefListStartIndex = 7;
           if (Version >= 6) {
             NumRefsIndex = 6;
-            EntryCount = Record[5];
             RefListStartIndex = 8;
             if (Version >= 7) {
               RefListStartIndex = 9;