update dependency to lsp4e to version 0.21.0 since the corresponding API is required

Author: martinlippert

eclipse-language-servers/org.springframework.tooling.boot.ls/META-INF/MANIFEST.MF

@@ -12,9 +12,9 @@ Require-Bundle: org.eclipse.jdt.launching;bundle-version="3.9.0",
  org.eclipse.jdt.ui;bundle-version="3.13.0",
  org.eclipse.tm4e.core;bundle-version="0.1.0",
  org.eclipse.tm4e.ui;bundle-version="0.1.0",
- org.eclipse.lsp4e;bundle-version="0.13.1.202003021135",
- org.eclipse.lsp4j;bundle-version="0.9.0",
- org.eclipse.lsp4j.jsonrpc;bundle-version="0.9.0",
+ org.eclipse.lsp4e;bundle-version="0.21.0",
+ org.eclipse.lsp4j;bundle-version="0.19.0",
+ org.eclipse.lsp4j.jsonrpc;bundle-version="0.19.0",
  org.eclipse.ui.workbench,
  org.eclipse.jface,
  org.springframework.tooling.ls.eclipse.commons;bundle-version="0.2.0",