ClangCodeModel: Remove fallback code for clangd < 13

Amends 4dfdbf91f6.

Change-Id: Ie8657329380e83aeb76503e360afa5ebf0e60fbb
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -1708,8 +1708,7 @@ void ClangdClient::Private::handleFindUsagesResult(quint64 key, const QList<Loca
     }
 
     qCDebug(clangdLog) << "document count is" << refData->fileData.size();
-    if (refData->replacementData || q->versionNumber() < QVersionNumber(13)
-            || !refData->categorize) {
+    if (refData->replacementData || !refData->categorize) {
         qCDebug(clangdLog) << "skipping AST retrieval";
         reportAllSearchResultsAndFinish(*refData);
         return;
@@ -1879,11 +1878,6 @@ void ClangdClient::followSymbol(TextDocument *document,
     };
     symbolSupport().findLinkAt(document, adjustedCursor, std::move(gotoDefCallback), true);
 
-    if (versionNumber() < QVersionNumber(12)) {
-        d->followSymbolData->cursorNode.emplace(AstNode());
-        return;
-    }
-
     const auto astHandler = [this, id = d->followSymbolData->id]
             (const AstNode &ast, const MessageId &) {
         qCDebug(clangdLog) << "received ast response for cursor";

src/plugins/clangcodemodel/clangfollowsymbol.cpp

@@ -260,7 +260,7 @@ void ClangFollowSymbol::switchDeclDef(const CppEditor::CursorInEditor &data,
 {
     ClangdClient * const client
             = ClangModelManagerSupport::instance()->clientForFile(data.filePath());
-    if (client && client->isFullyIndexed() && client->versionNumber() >= QVersionNumber(13)) {
+    if (client && client->isFullyIndexed()) {
         client->switchDeclDef(data.textDocument(), data.cursor(), data.editorWidget(),
                               std::move(processLinkCallback));
         return;

src/plugins/clangcodemodel/test/clangdtests.cpp

@@ -179,7 +179,6 @@ ClangdTestFindReferences::ClangdTestFindReferences()
 {
     setProjectFileName("find-usages.pro");
     setSourceFileNames({"defs.h", "main.cpp"});
-    setMinimumVersion(13);
 }
 
 void ClangdTestFindReferences::initTestCase()
@@ -322,7 +321,6 @@ ClangdTestFollowSymbol::ClangdTestFollowSymbol()
 {
     setProjectFileName("follow-symbol.pro");
     setSourceFileNames({"main.cpp", "header.h"});
-    setMinimumVersion(12);
 }
 
 void ClangdTestFollowSymbol::test_data()
@@ -409,7 +407,6 @@ ClangdTestLocalReferences::ClangdTestLocalReferences()
 {
     setProjectFileName("local-references.pro");
     setSourceFileNames({"references.cpp"});
-    setMinimumVersion(13);
 }
 
 // We currently only support local variables, but if and when clangd implements
@@ -525,7 +522,6 @@ ClangdTestTooltips::ClangdTestTooltips()
 {
     setProjectFileName("tooltips.pro");
     setSourceFileNames({"tooltips.cpp"});
-    setMinimumVersion(13);
 }
 
 void ClangdTestTooltips::test_data()
@@ -668,7 +664,6 @@ ClangdTestHighlighting::ClangdTestHighlighting()
 {
     setProjectFileName("highlighting.pro");
     setSourceFileNames({"highlighting.cpp"});
-    setMinimumVersion(13);
 }
 
 void ClangdTestHighlighting::initTestCase()