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/script/signingprovider.cpp

@@ -368,7 +368,7 @@ void TaprootBuilder::Insert(TaprootBuilder::NodeInfo&& node, int depth)
     return branch.size() == 0 || (branch.size() == 1 && branch[0]);
 }
 
-TaprootBuilder& TaprootBuilder::Add(int depth, Span<const unsigned char> script, int leaf_version, bool track)
+TaprootBuilder& TaprootBuilder::Add(int depth, std::span<const unsigned char> script, int leaf_version, bool track)
 {
     assert((leaf_version & ~TAPROOT_LEAF_MASK) == 0);
     if (!IsValid()) return *this;