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ARROW-11187: [Rust] [Parquet] Fix Build error by Pin specific parquet-format-rs version

parquet-format 2.7.0 was released yesterday, and our cargo.toml file specifies 2.6.1, which means cargo will update this on new builds or of you run `cargo update`

```
alamb@ip-192-168-0-182:~/Software/arrow2/rust$ cargo update
cargo update
    Updating crates.io index
    Updating parquet-format v2.6.1 -> v2.7.0
```

Sadly this version of new parquet format causes a build error:

```
157 Compiling arrow-flight v3.0.0-SNAPSHOT (/__w/arrow/arrow/rust/arrow-flight)
 158error[E0063]: missing fields `file_offset`, `ordinal`, `total_compressed_size` in initializer of `RowGroup`
 159 --> parquet/src/file/metadata.rs:262:9
 160 |
 161262 | RowGroup {
 162 | ^^^^^^^^ missing `file_offset`, `ordinal`, `total_compressed_size`
 163
 164error[E0063]: missing field `bloom_filter_offset` in initializer of `ColumnMetaData`
 165 --> parquet/src/file/metadata.rs:501:31
 166 |
 167501 | let column_metadata = ColumnMetaData {
 168 | ^^^^^^^^^^^^^^ missing `bloom_filter_offset`
 169
 170error[E0063]: missing fields `crypto_metadata`, `encrypted_column_metadata` in initializer of `ColumnChunk`
 171 --> parquet/src/file/metadata.rs:517:9
 172 |
 173517 | ColumnChunk {
 174 | ^^^^^^^^^^^ missing `crypto_metadata`, `encrypted_column_metadata`
 175
```

This PR pins the version so that it will not pick up 2.7

Closes #9138 from nevi-me/ARROW-11187

Authored-by: Neville Dipale <nevilledips@gmail.com>
Signed-off-by: Andrew Lamb <andrew@nerdnetworks.org>