[lldb] NFC: Fix trivial typo in comments, documents, and messages

Differential Revision: https://reviews.llvm.org/D77460

lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp

@@ -1044,7 +1044,7 @@ std::string PythonException::ReadBacktrace() const {
   if (!backtrace) {
     std::string message =
         std::string(toCString()) + "\n" +
-        "Traceback unavailble, an error occurred while reading it:\n";
+        "Traceback unavailable, an error occurred while reading it:\n";
     return (message + llvm::toString(backtrace.takeError()));
   }