bootstat: avoid vector<const T>

A container of const T uses std::allocator<const T>, which was an
undocumented libc++ extension that has been removed.

See https://github.com/llvm/llvm-project/pull/96319.

Bug: 349681543
Test: m bootstat
Change-Id: Id338f439aa4caf8c9f3c6fc15faef19b1edc4368
diff --git a/bootstat/bootstat.cpp b/bootstat/bootstat.cpp
index d402bf1..d476d36 100644
--- a/bootstat/bootstat.cpp
+++ b/bootstat/bootstat.cpp
@@ -499,7 +499,7 @@
 }
 
 // Canonical list of supported primary reboot reasons.
-const std::vector<const std::string> knownReasons = {
+const std::vector<std::string> knownReasons = {
     // clang-format off
     // kernel
     "watchdog",