scripted-diff: Use std::span over Span

-BEGIN VERIFY SCRIPT-

 ren() { sed -i "s!\<$1\>!$2!g" $( git grep -l "$1" -- "./src" ":(exclude)src/span.h" ":(exclude)src/leveldb/db/log_test.cc" ) ; }

 ren Span            std::span
 ren AsBytes         std::as_bytes
 ren AsWritableBytes std::as_writable_bytes

 sed -i 's!SpanPopBack(Span!SpanPopBack(std::span!g' ./src/span.h

-END VERIFY SCRIPT-

src/test/pool_tests.cpp

@@ -90,7 +90,7 @@ BOOST_AUTO_TEST_CASE(allocate_any_byte)
 
     uint8_t num_allocs = 200;
 
-    auto data = std::vector<Span<uint8_t>>();
+    auto data = std::vector<std::span<uint8_t>>();
 
     // allocate an increasing number of bytes
     for (uint8_t num_bytes = 0; num_bytes < num_allocs; ++num_bytes) {