Fix uncaught-exception.test. (#146190)

See https://github.com/llvm/llvm-project/pull/125924
To match a literal plus sign, it must be escaped with a backslash (`\`).

GitOrigin-RevId: 3923dd4484b8a46295b1ce0711e9bcb35cc19c09

test/fuzzer/uncaught-exception.test

diff --git a/test/fuzzer/uncaught-exception.test b/test/fuzzer/uncaught-exception.test
index 9840010..264bb5d 100644
--- a/test/fuzzer/uncaught-exception.test
+++ b/test/fuzzer/uncaught-exception.test
@@ -8,4 +8,4 @@
 # For example, msvc fails with 'uncaught C++ exception'. So the error we check depends on the compiler target.
 RUN: not %run %t-UncaughtException 2>&1 | FileCheck %s
 
-CHECK: ERROR: libFuzzer: {{deadly signal|uncaught C++ exception}}
+CHECK: ERROR: libFuzzer: {{deadly signal|uncaught C\+\+ exception}}