[clang] Fix a typo in documentation (#143169)

Author: kazutakahirata

clang/docs/ReleaseNotes.rst

@@ -850,7 +850,7 @@ Miscellaneous Clang Crashes Fixed
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Fixed crash when ``-print-stats`` is enabled in compiling IR files. (#GH131608)
-- Fix code completion crash involving PCH serialzied templates. (#GH139019)
+- Fix code completion crash involving PCH serialized templates. (#GH139019)
 
 OpenACC Specific Changes
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