Fix comment in Converter.

Converter.apply is annotated as returning null, so it's sound. The LegacyConverter problem arises only if users view the converter as a Function<A, B>, since Function<A, B>.apply is *not* annotated as returning null (and yet a LegacyConverter may do so, even given a non-null input).

RELNOTES=n/a
PiperOrigin-RevId: 368219982

android/guava/src/com/google/common/base/Converter.java

@@ -234,11 +234,11 @@ A correctedDoBackward(@CheckForNull B b) {
    * methods as implementations of normal converters do?
    *
    * But no matter what we do, it's worth remembering that the resulting code is going to be unsound
-   * in the presence of LegacyConverter, at least in the case of Converter.apply and convertAll (and
-   * for any checkers that apply @PolyNull-like semantics to Converter.convert). So maybe we don't
-   * want to think too hard about how to prevent our checkers from issuing errors related to
-   * LegacyConverter, since it turns out that LegacyConverter does violate the assumptions we make
-   * elsewhere.
+   * in the presence of LegacyConverter, at least in the case of users who view the converter as a
+   * Function<A, B> or who call convertAll (and for any checkers that apply @PolyNull-like semantics
+   * to Converter.convert). So maybe we don't want to think too hard about how to prevent our
+   * checkers from issuing errors related to LegacyConverter, since it turns out that
+   * LegacyConverter does violate the assumptions we make elsewhere.
    */
 
   @CheckForNull

guava/src/com/google/common/base/Converter.java

@@ -234,11 +234,11 @@ A correctedDoBackward(@CheckForNull B b) {
    * methods as implementations of normal converters do?
    *
    * But no matter what we do, it's worth remembering that the resulting code is going to be unsound
-   * in the presence of LegacyConverter, at least in the case of Converter.apply and convertAll (and
-   * for any checkers that apply @PolyNull-like semantics to Converter.convert). So maybe we don't
-   * want to think too hard about how to prevent our checkers from issuing errors related to
-   * LegacyConverter, since it turns out that LegacyConverter does violate the assumptions we make
-   * elsewhere.
+   * in the presence of LegacyConverter, at least in the case of users who view the converter as a
+   * Function<A, B> or who call convertAll (and for any checkers that apply @PolyNull-like semantics
+   * to Converter.convert). So maybe we don't want to think too hard about how to prevent our
+   * checkers from issuing errors related to LegacyConverter, since it turns out that
+   * LegacyConverter does violate the assumptions we make elsewhere.
    */
 
   @CheckForNull