[mlir][Transforms][NFC] Dialect conversion: Fix typo and improve docs (llvm#107539)

Author: matthias-springer

mlir/docs/DialectConversion.md

@@ -383,6 +383,11 @@ class TypeConverter {
 };
 ```
 
+Materializations through the type converter are optional. If the
+`ConversionConfig::buildMaterializations` flag is set to "false", the dialect
+conversion driver builds an `unrealized_conversion_cast` op instead of calling
+the respective type converter callback whenever a materialization is required.
+
 ### Region Signature Conversion
 
 From the perspective of type conversion, the types of block arguments are a bit

mlir/include/mlir/Transforms/DialectConversion.h

@@ -1127,13 +1127,12 @@ struct ConversionConfig {
 
   /// If set to "true", the dialect conversion attempts to build source/target/
   /// argument materializations through the type converter API in lieu of
-  /// builtin.unrealized_conversion_cast ops. The conversion process fails if
+  /// "builtin.unrealized_conversion_cast ops". The conversion process fails if
   /// at least one materialization could not be built.
   ///
-  /// If set to "false", the dialect conversion does not does not build any
-  /// custom materializations and instead inserts
-  /// builtin.unrealized_conversion_cast ops to ensure that the resulting IR
-  /// is valid.
+  /// If set to "false", the dialect conversion does not build any custom
+  /// materializations and instead inserts "builtin.unrealized_conversion_cast"
+  /// ops to ensure that the resulting IR is valid.
   bool buildMaterializations = true;
 };