MINOR: [Docs] Fix a typo in overview.rst (#48678)

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### Rationale for this change
This PR fixes a typo in `overview.rst`

### What changes are included in this PR?
`most of implementation` -> `most of the implementations`

### Are these changes tested?
CI

### Are there any user-facing changes?
yes, doc-only change

Authored-by: Ruifeng Zheng <ruifengz@apache.org>
Signed-off-by: Nic Crane <thisisnic@gmail.com>

Author: zhengruifeng

docs/source/developers/overview.rst

@@ -202,7 +202,7 @@ Endianness
 ++++++++++
 
 The Arrow format allows setting endianness.  Due to the popularity of
-little endian architectures most of implementation assume little endian by
+little endian architectures, most of the implementations assume little endian by
 default. There has been some  effort to support big endian platforms as well.
 Based on a `mailing-list discussion
 <https://mail-archives.apache.org/mod_mbox/arrow-dev/202009.mbox/%3cCAK7Z5T--HHhr9Dy43PYhD6m-XoU4qoGwQVLwZsG-kOxXjPTyZA@mail.gmail.com%3e>`__,