[core] Fix performance-noexcept-move-constructor errors

As reported by clang-tidy-8.

platform/default/include/mbgl/storage/sqlite3.hpp

@@ -79,9 +79,9 @@ public:
     static mapbox::util::variant<Database, Exception> tryOpen(const std::string &filename, int flags = 0);
     static Database open(const std::string &filename, int flags = 0);
 
-    Database(Database &&);
+    Database(Database&&) noexcept;
     ~Database();
-    Database &operator=(Database &&);
+    Database& operator=(Database&&) noexcept;
 
     void setBusyTimeout(std::chrono::milliseconds);
     void exec(const std::string &sql);

platform/default/src/mbgl/storage/sqlite3.cpp

@@ -144,10 +144,9 @@ Database::Database(std::unique_ptr<DatabaseImpl> impl_)
     : impl(std::move(impl_))
 {}
 
-Database::Database(Database &&other)
-    : impl(std::move(other.impl)) {}
+Database::Database(Database&& other) noexcept : impl(std::move(other.impl)) {}
 
-Database &Database::operator=(Database &&other) {
+Database& Database::operator=(Database&& other) noexcept {
     std::swap(impl, other.impl);
     return *this;
 }