Remove always passing DCHECK.

const_header_lines_iterator.idx_ is of type HeaderLines::size_type,
and HeaderLines is a std::vector, which can reasonably be expected to be
unsigned, therefore the DCHECK always passes.

This line causes compilation to fail in Envoy with GCC with error
"comparison of unsigned expression >= 0 is always true [-Werror=type-limits]".

PiperOrigin-RevId: 448264499

quiche/balsa/balsa_headers.h

diff --git a/quiche/balsa/balsa_headers.h b/quiche/balsa/balsa_headers.h
index 8ed2f11..ad51cb8 100644
--- a/quiche/balsa/balsa_headers.h
+++ b/quiche/balsa/balsa_headers.h
@@ -1337,7 +1337,6 @@
 inline void BalsaHeaders::erase(const const_header_lines_iterator& it) {
   QUICHE_DCHECK_EQ(it.headers_, this);
   QUICHE_DCHECK_LT(it.idx_, header_lines_.size());
-  QUICHE_DCHECK_GE(it.idx_, 0u);
   header_lines_[it.idx_].skip = true;
 }