Snippet completions appear when they shouldn't (when normal completions don't appear)

Type "namespace tr". This incorrectly causes the "try" snippet to get invoked. To fix this, we would need to move the snippet implementation/data from cpp_snippets.json to after our lexer gets used to exclude incorrect completions.

Fixed with our latest 0.21.0-insiders3. Setting C_Cpp.updateChannel to "Insiders" is another way to get the update.