Misspellling: "occurance" --> "occurrence"

Doc/lib/libre.tex

@@ -447,7 +447,7 @@ Return the string obtained by replacing the leftmost non-overlapping
 occurrences of \var{pattern} in \var{string} by the replacement
 \var{repl}.  If the pattern isn't found, \var{string} is returned
 unchanged.  \var{repl} can be a string or a function; if a function,
-it is called for every non-overlapping occurance of \var{pattern}.
+it is called for every non-overlapping occurrence of \var{pattern}.
 The function takes a single match object argument, and returns the
 replacement string.  For example: