Fix a typo

Author: mortenpi

pdf/make.jl

@@ -40,7 +40,7 @@ end
 function makedocs(julia_exec)
     @sync begin
         builder = @async begin
-            withenv(DOCUMENTER_KEY" => nothing, # skips deploydocs with the BuildBotConfig (see doc/make.jl)
+            withenv("DOCUMENTER_KEY" => nothing, # skips deploydocs with the BuildBotConfig (see doc/make.jl)
                     "BUILDROOT" => nothing) do
                 run(`make -C $(JULIA_SOURCE)/doc pdf texplatform=docker JULIA_EXECUTABLE=$(julia_exec)`)
             end