Reverts let chain usage because not supported until rust 2024 (#1525)

# Description

@swift-nav/algint-team

minor change to rust conditional stuff

# API compatibility

Does this change introduce a API compatibility risk?

No

## API compatibility plan

If the above is "Yes", please detail the compatibility (or migration)
plan:

None

# JIRA Reference

n/a done to unblock a release

Author: pcrumley

rust/sbp/Cargo.toml

@@ -55,7 +55,7 @@ version = "0.4"
 optional = true
 
 [dependencies.base64]
-version = "0.13"
+version = "0.22"
 optional = true
 
 [dependencies.futures]

rust/sbp/src/sbp_string.rs

@@ -101,11 +101,10 @@ impl SbpString<Vec<u8>, DoubleNullTerminated> {
         data: impl Into<Vec<u8>>,
     ) -> Result<Self, DoubleNullTerminatedError> {
         let vec = data.into();
-        if let [.., two, one] = vec.as_slice()
-            && two == &0
-            && one == &0
-        {
-            return Ok(SbpString::new(vec));
+        if let [.., two, one] = vec.as_slice() {
+            if two == &0 && one == &0 {
+                return Ok(SbpString::new(vec));
+            }
         };
         Err(DoubleNullTerminatedError)
     }