GH-38952: [Format] Fix spelling (#38953)

### Rationale for this change

### What changes are included in this PR?

Spelling fixes to format/

### Are these changes tested?

### Are there any user-facing changes?

* Closes: #38952

Authored-by: Josh Soref <2119212+jsoref@users.noreply.github.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

format/Schema.fbs

@@ -372,7 +372,7 @@ table Time {
 /// no indication of how to map this information to a physical point in time.
 /// Naive date-times must be handled with care because of this missing
 /// information, and also because daylight saving time (DST) may make
-/// some values ambiguous or non-existent. A naive date-time may be
+/// some values ambiguous or nonexistent. A naive date-time may be
 /// stored as a struct with Date and Time fields. However, it may also be
 /// encoded into a Timestamp column with an empty timezone. The timestamp
 /// values should be computed "as if" the timezone of the date-time values

format/adbc.h

@@ -475,7 +475,7 @@ struct ADBC_EXPORT AdbcError {
 /// Must be kept alive as long as any connections exist.
 struct ADBC_EXPORT AdbcDatabase {
   /// \brief Opaque implementation-defined state.
-  /// This field is NULLPTR iff the connection is unintialized/freed.
+  /// This field is NULLPTR iff the connection is uninitialized/freed.
   void* private_data;
   /// \brief The associated driver (used by the driver manager to help
   ///   track state).
@@ -498,7 +498,7 @@ struct ADBC_EXPORT AdbcDatabase {
 /// serialize accesses to a connection.
 struct ADBC_EXPORT AdbcConnection {
   /// \brief Opaque implementation-defined state.
-  /// This field is NULLPTR iff the connection is unintialized/freed.
+  /// This field is NULLPTR iff the connection is uninitialized/freed.
   void* private_data;
   /// \brief The associated driver (used by the driver manager to help
   ///   track state).
@@ -536,7 +536,7 @@ struct ADBC_EXPORT AdbcConnection {
 /// serialize accesses to a statement.
 struct ADBC_EXPORT AdbcStatement {
   /// \brief Opaque implementation-defined state.
-  /// This field is NULLPTR iff the connection is unintialized/freed.
+  /// This field is NULLPTR iff the connection is uninitialized/freed.
   void* private_data;
 
   /// \brief The associated driver (used by the driver manager to help
@@ -575,7 +575,7 @@ struct AdbcPartitions {
   const size_t* partition_lengths;
 
   /// \brief Opaque implementation-defined state.
-  /// This field is NULLPTR iff the connection is unintialized/freed.
+  /// This field is NULLPTR iff the connection is uninitialized/freed.
   void* private_data;
 
   /// \brief Release the contained partitions.
@@ -603,11 +603,11 @@ struct AdbcPartitions {
 /// worrying about multiple definitions of the same symbol.
 struct ADBC_EXPORT AdbcDriver {
   /// \brief Opaque driver-defined state.
-  /// This field is NULL if the driver is unintialized/freed (but
+  /// This field is NULL if the driver is uninitialized/freed (but
   /// it need not have a value even if the driver is initialized).
   void* private_data;
   /// \brief Opaque driver manager-defined state.
-  /// This field is NULL if the driver is unintialized/freed (but
+  /// This field is NULL if the driver is uninitialized/freed (but
   /// it need not have a value even if the driver is initialized).
   void* private_manager;