Fix CI failures: remove 'in' keyword triggering FS3885 and add XLF entries

- Remove explicit 'in' keyword in HashMultiMap.fs and fsi.fs that
  triggered the new FS3885 warning (treated as error in CI builds)
- Add missing XLF translation entries for featureWarnOnLetInSequenceExpression
  and tcLetExpressionWithInHasMultiLineBody to all 13 locale files

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: T-Gro

src/Compiler/Interactive/fsi.fs

@@ -1532,7 +1532,7 @@ type internal FsiConsoleInput
 
     /// Try to get the first line, if we snarfed it while probing.
     member _.TryGetFirstLine() =
-        let r = firstLine in
+        let r = firstLine
         firstLine <- None
         r
 

src/Compiler/Utilities/HashMultiMap.fs

@@ -169,7 +169,7 @@ type internal HashMultiMap<'Key, 'Value when 'Key: not null>(size: int, comparer
             | _ -> false
 
         member s.Remove(k: 'Key) =
-            let res = s.ContainsKey(k) in
+            let res = s.ContainsKey(k)
             s.Remove(k)
             res