fix: @[nospecialize] is never template-like (#12663)

This PR avoids false-positive error messages on specialization
restrictions under the module system when the declaration is explicitly
marked as not specializable. It could also provide some minor public
size and rebuild savings.

src/Lean/Compiler/LCNF/Basic.lean

@@ -1017,7 +1017,7 @@ Return `true` if `decl` is supposed to be inlined/specialized.
 -/
 def Decl.isTemplateLike (decl : Decl pu) : CoreM Bool := do
   let env ← getEnv
-  if ← hasLocalInst decl.type then
+  if !hasNospecializeAttribute env decl.name && (← hasLocalInst decl.type) then
     return true -- `decl` applications will be specialized
   else if (← isImplicitReducible decl.name) then
     return true -- `decl` is "fuel" for code specialization