[analyzer][docs] Fix typo in checker name

Fixes #55720

Author: Balazs Benics

clang/docs/analyzer/checkers.rst

@@ -947,9 +947,9 @@ Check the size argument passed into C string functions for common erroneous patt
      // warn: potential buffer overflow
  }
 
-.. _unix-cstrisng-NullArg:
+.. _unix-cstring-NullArg:
 
-unix.cstrisng.NullArg (C)
+unix.cstring.NullArg (C)
 """""""""""""""""""""""""
 Check for null pointers being passed as arguments to C string functions:
 ``strlen, strnlen, strcpy, strncpy, strcat, strncat, strcmp, strncmp, strcasecmp, strncasecmp``.