"Remove redundant backticks": Fix false positive for underscore

#KT-28592 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/RemoveRedundantBackticksInspection.kt

@@ -46,7 +46,7 @@ class RemoveRedundantBackticksInspection : AbstractKotlinInspection() {
     }
 
     private fun isKeyword(text: String): Boolean {
-        return text == "yield" || (KtTokens.KEYWORDS.types + KtTokens.SOFT_KEYWORDS.types).any { it.toString() == text }
+        return text == "yield" || text == "_" || (KtTokens.KEYWORDS.types + KtTokens.SOFT_KEYWORDS.types).any { it.toString() == text }
     }
 
     private fun isRedundantBackticks(node: ASTNode): Boolean {

idea/testData/inspectionsLocal/removeRedundantBackticks/underscore.kt

@@ -0,0 +1,8 @@
+// PROBLEM: none
+
+fun test() {
+    try {
+    } catch (_: Throwable) {
+        <caret>`_`.printStackTrace()
+    }
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -5474,6 +5474,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/removeRedundantBackticks/property.kt");
         }
 
+        @TestMetadata("underscore.kt")
+        public void testUnderscore() throws Exception {
+            runTest("idea/testData/inspectionsLocal/removeRedundantBackticks/underscore.kt");
+        }
+
         @TestMetadata("yield.kt")
         public void testYield() throws Exception {
             runTest("idea/testData/inspectionsLocal/removeRedundantBackticks/yield.kt");