[scudo] Remove internal linkage from LargeBlock header helpers (NFC) (#207708)

`addHeaderTag` and `getHeader` are static function templates in
`secondary.h,` so any TU that includes the header without using them
trips `-Wunused-template`. Dropping static fixes the warning.

Part of #202945.

GitOrigin-RevId: dcf969eaf2c25048542d13946ca5ff65be5bc7ab

secondary.h

diff --git a/secondary.h b/secondary.h
index 26c45cc..b4a5685 100644
--- a/secondary.h
+++ b/secondary.h
@@ -56,17 +56,17 @@
 
 constexpr uptr getHeaderSize() { return sizeof(Header); }
 
-template <typename Config> static uptr addHeaderTag(uptr Ptr) {
+template <typename Config> uptr addHeaderTag(uptr Ptr) {
   if (allocatorSupportsMemoryTagging<Config>())
     return addFixedTag(Ptr, 1);
   return Ptr;
 }
 
-template <typename Config> static Header *getHeader(uptr Ptr) {
+template <typename Config> Header *getHeader(uptr Ptr) {
   return reinterpret_cast<Header *>(addHeaderTag<Config>(Ptr)) - 1;
 }
 
-template <typename Config> static Header *getHeader(const void *Ptr) {
+template <typename Config> Header *getHeader(const void *Ptr) {
   return getHeader<Config>(reinterpret_cast<uptr>(Ptr));
 }