Fix "manfiest" typos in error message and comments (#2316)

(cherry picked from commit 9750a21, PR #2316)

Author: devmotion

src/manifest.jl

@@ -96,7 +96,7 @@ function normalize_deps(name, uuid, deps::Vector{String}, manifest::Dict{String,
                      "but no such entry exists in the manifest.")
         end
         # should have used dict format instead of vector format
-        length(infos) == 1 || pkgerror("Invalid manfiest format. ",
+        length(infos) == 1 || pkgerror("Invalid manifest format. ",
                                        "`$name=$uuid`'s dependency on `$dep` is ambiguous.")
         final[dep] = infos[1].uuid
     end

test/new.jl

@@ -1259,7 +1259,7 @@ end
         @test haskey(Pkg.project().dependencies, "Example")
         @test haskey(Pkg.project().dependencies, "Unicode")
     end end
-    # `instantiate` lonely manfiest
+    # `instantiate` lonely manifest
     isolate(loaded_depot=true) do
         manifest_dir = joinpath(@__DIR__, "manifest", "noproject")
         cd(manifest_dir) do
@@ -1946,7 +1946,7 @@ end
     # Manifest Status API
     isolate(loaded_depot=true) do
         io = PipeBuffer()
-        ## empty manfiest
+        ## empty manifest
         Pkg.status(;io=io, mode=Pkg.PKGMODE_MANIFEST)
         @test occursin(r"Status `.+Manifest\.toml` \(empty manifest\)", readline(io))
         # loaded manifest