workflows/release-tasks: Remove stray backslash

Reviewed By: thieta

Differential Revision: https://reviews.llvm.org/D150018

(cherry picked from commit afa607f)

Author: tstellar

.github/workflows/release-tasks.yml

@@ -22,7 +22,7 @@ jobs:
 
     - name: Install Dependencies
       run: |
-        sudo apt-get update \
+        sudo apt-get update
         sudo apt-get install -y \
             doxygen \
             graphviz \