PR #1720: Fix spelling mistake: occurrance -> occurrence

Imported from GitHub PR #1720

Merge a72c4bc into 0598e58

Merging this change closes #1720

COPYBARA_INTEGRATE_REVIEW=#1720 from eltociear:patch-1 a72c4bc
PiperOrigin-RevId: 653737423
Change-Id: I5638538d1b008942feba6dc6fc98dcdbf53653ef

absl/strings/cord.h

@@ -772,7 +772,7 @@ class Cord {
 
   // Cord::Find()
   //
-  // Returns an iterator to the first occurrance of the substring `needle`.
+  // Returns an iterator to the first occurrence of the substring `needle`.
   //
   // If the substring `needle` does not occur, `Cord::char_end()` is returned.
   CharIterator Find(absl::string_view needle) const;