Fix "the the" typo in documentation and user facing strings

There are many more instances of this pattern, but I chose to limit this change to .rst files (docs), anything in libcxx/include, and string literals. These have the highest chance of being seen by end users.

Reviewed By: #libc, Mordante, martong, ldionne

Differential Revision: https://reviews.llvm.org/D124708

NOKEYCHECK=True
GitOrigin-RevId: 87a55137e2a2a6684a20223494ad46d2fa33aca8
diff --git a/src/filesystem/operations.cpp b/src/filesystem/operations.cpp
index 562cd8b..7467abb 100644
--- a/src/filesystem/operations.cpp
+++ b/src/filesystem/operations.cpp
@@ -1884,7 +1884,7 @@
   if (ElemCount == 0 && (PP.atEnd() || *PP == PATHSTR("")))
     return PATHSTR(".");
 
-  // return a path constructed with 'n' dot-dot elements, followed by the the
+  // return a path constructed with 'n' dot-dot elements, followed by the
   // elements of '*this' after the mismatch.
   path Result;
   // FIXME: Reserve enough room in Result that it won't have to re-allocate.