Revert "'yield' reserved as a keyword"

This reverts commit 434082cadb.

j2k/testData/fileOrElement/identifier/keywords.java

@@ -1,2 +1,2 @@
 //statement
-int as, type, val, var, fun, is, in, object, when, yield, typeof;
+int as, type, val, var, fun, is, in, object, when, typeof;

j2k/testData/fileOrElement/identifier/keywords.kt

@@ -7,5 +7,4 @@ val `is`: Int
 val `in`: Int
 val `object`: Int
 val `when`: Int
-val `yield`: Int
-val `typeof`: Int
+val `typeof`: Int

j2k/testData/fileOrElement/importStatement/importWithKeywords.java

@@ -1,6 +1,6 @@
 //file
 package test;
 
-import as.type.val.var.fun.is.in.object.when.yield.typeof;
+import as.type.val.var.fun.is.in.object.when.typeof;
 
-class Test {}
+class Test {}

j2k/testData/fileOrElement/importStatement/importWithKeywords.kt

@@ -1,6 +1,6 @@
 // ERROR: Unresolved reference: `as`
 package test
 
-import `as`.type.`val`.`var`.`fun`.`is`.`in`.`object`.`when`.`yield`.`typeof`
+import `as`.type.`val`.`var`.`fun`.`is`.`in`.`object`.`when`.`typeof`
 
-internal class Test
+internal class Test