Fix spelling and grammar in fbcode/eden/fs comments, docs, and Thrift

Summary:
Improve readability and accuracy by correcting typos, duplicate words, and minor grammar issues across EdenFS comments, documentation, and Thrift docstrings. This reduces confusion and keeps docs consistent for developers, with no functional code changes or behavior impact.

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AI generated Summary & Test Plan from DEV93655210

Differential Revision: D95213995

fbshipit-source-id: 4319a3e39ff4ced4d7e58d7a4d2722a73e1cf27a

Author: Liubov Dmitrieva

third-party/watchman/src/eden/fs/service/eden.thrift

@@ -450,7 +450,7 @@ union Sha1OrError {
  * 2. Directories: POSIX_ERROR, EISDIR
  * 3. Non-source-control file types (FIFO, socket, char, block, whiteout, etc.): POSIX_ERROR, EINVAL
  * 4. Non-existent files: POSIX_ERROR, ENOENT
- * 5. Files that that lack blake3 hashes: ATTRIBUTES_UNAVAILABLE, ENOENT
+ * 5. Files that lack blake3 hashes: ATTRIBUTES_UNAVAILABLE, ENOENT
  */
 union Blake3OrError {
   1: BinaryHash blake3;
@@ -504,7 +504,7 @@ union ObjectIdOrError {
  * 1. Symlinks: POSIX_ERROR, EINVAL
  * 2. Non-source-control file types (FIFO, socket, char, block, whiteout, etc.): POSIX_ERROR, EINVAL
  * 3. Non-existent files: POSIX_ERROR, ENOENT
- * 4. Files that that lack digest sizes: ATTRIBUTES_UNAVAILABLE, ENOENT
+ * 4. Files that lack digest sizes: ATTRIBUTES_UNAVAILABLE, ENOENT
  * 5. Materialized (locally modified) directories: ATTRIBUTES_UNAVAILABLE, ENOENT
  */
 union DigestSizeOrError {
@@ -518,7 +518,7 @@ union DigestSizeOrError {
  * 1. Symlinks: POSIX_ERROR, EINVAL
  * 2. Non-source-control file types (FIFO, socket, char, block, whiteout, etc.): POSIX_ERROR, EINVAL
  * 3. Non-existent files: POSIX_ERROR, ENOENT
- * 4. Files/dirs that that lack digest hashes: ATTRIBUTES_UNAVAILABLE, ENOENT
+ * 4. Files/dirs that lack digest hashes: ATTRIBUTES_UNAVAILABLE, ENOENT
  * 5. Materialized (locally modified) directories: ATTRIBUTES_UNAVAILABLE, ENOENT
  */
 union DigestHashOrError {