Remove redundant backticks: do not report if variable inside the string and isn't followed by space

#KT-35051 Fixed

idea/testData/inspectionsLocal/removeRedundantBackticks/inStringTemplate.kt

@@ -0,0 +1,5 @@
+// PROBLEM: none
+fun main() {
+    val name = "Kotlin"
+    val test = "$<caret>`name`test"
+}

idea/testData/inspectionsLocal/removeRedundantBackticks/inStringTemplate2.kt

@@ -0,0 +1,4 @@
+fun main() {
+    val name = "Kotlin"
+    val test = "$<caret>`name` test"
+}

idea/testData/inspectionsLocal/removeRedundantBackticks/inStringTemplate2.kt.after

@@ -0,0 +1,4 @@
+fun main() {
+    val name = "Kotlin"
+    val test = "$name test"
+}

idea/testData/inspectionsLocal/removeRedundantBackticks/inStringTemplate3.kt

@@ -0,0 +1,4 @@
+fun main() {
+    val name = "Kotlin"
+    val test = "${<caret>`name`}test"
+}

idea/testData/inspectionsLocal/removeRedundantBackticks/inStringTemplate3.kt.after

@@ -0,0 +1,4 @@
+fun main() {
+    val name = "Kotlin"
+    val test = "${name}test"
+}