[khmer] Fix comment

Fixes https://github.com/harfbuzz/harfbuzz/issues/3104

src/hb-ot-shape-complex-indic.cc

@@ -106,7 +106,8 @@ indic_features[] =
 {
   /*
    * Basic features.
-   * These features are applied in order, one at a time, after initial_reordering.
+   * These features are applied in order, one at a time, after initial_reordering,
+   * constrained to the syllable.
    */
   {HB_TAG('n','u','k','t'), F_GLOBAL_MANUAL_JOINERS},
   {HB_TAG('a','k','h','n'), F_GLOBAL_MANUAL_JOINERS},
@@ -121,8 +122,8 @@ indic_features[] =
   {HB_TAG('c','j','c','t'), F_GLOBAL_MANUAL_JOINERS},
   /*
    * Other features.
-   * These features are applied all at once, after final_reordering
+   * These features are applied all at once, after final_reordering, constrained
-   * but before clearing syllables.
+   * to the syllable.
    * Default Bengali font in Windows for example has intermixed
    * lookups for init,pres,abvs,blws features.
    */

src/hb-ot-shape-complex-khmer.cc

@@ -42,7 +42,8 @@ khmer_features[] =
 {
   /*
    * Basic features.
-   * These features are applied in order, one at a time, after reordering.
+   * These features are applied all at once, before reordering, constrained
+   * to the syllable.
    */
   {HB_TAG('p','r','e','f'), F_MANUAL_JOINERS},
   {HB_TAG('b','l','w','f'), F_MANUAL_JOINERS},

src/hb-ot-shape-complex-myanmar.cc

@@ -41,7 +41,8 @@ myanmar_basic_features[] =
 {
   /*
    * Basic features.
-   * These features are applied in order, one at a time, after reordering.
+   * These features are applied in order, one at a time, after reordering,
+   * constrained to the syllable.
    */
   HB_TAG('r','p','h','f'),
   HB_TAG('p','r','e','f'),

src/hb-ot-shape-complex-use.cc

@@ -47,7 +47,8 @@ use_basic_features[] =
 {
   /*
    * Basic features.
-   * These features are applied all at once, before reordering.
+   * These features are applied all at once, before reordering, constrained
+   * to the syllable.
    */
   HB_TAG('r','k','r','f'),
   HB_TAG('a','b','v','f'),