Revert "allow finding stdlibs that are normal packages in the manifest but are now stdlibs" (#60101)

Author: KristofferC

base/loading.jl

@@ -463,8 +463,6 @@ function locate_package_env(pkg::PkgId, stopenv::Union{String, Nothing}=nothing)
             path = manifest_uuid_path(env, pkg)
             # missing is used as a sentinel to stop looking further down in envs
             if path === missing
-                # Before stopping, try stdlib fallback
-                is_stdlib(pkg) && @goto stdlib_fallback
                 path = nothing
                 @goto done
             end
@@ -476,7 +474,6 @@ function locate_package_env(pkg::PkgId, stopenv::Union{String, Nothing}=nothing)
                 stopenv == env && break
             end
         end
-        @label stdlib_fallback
         # Allow loading of stdlibs if the name/uuid are given
         # e.g. if they have been explicitly added to the project/manifest
         mbypath = manifest_uuid_path(Sys.STDLIB, pkg)

test/loading.jl

@@ -1537,21 +1537,12 @@ end
     mktempdir() do depot
         # This manifest has a LibGit2 entry that is missing LibGit2_jll, which should be
         # handled by falling back to the stdlib Project.toml for dependency truth.
-        badmanifest_test_dir = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps")
+        badmanifest_test_dir = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps.jl")
         @test success(addenv(
             `$(Base.julia_cmd()) --project=$badmanifest_test_dir --startup-file=no -e 'using LibGit2'`,
             "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
         ))
     end
-    mktempdir() do depot
-        # This manifest has a LibGit2 entry that has a LibGit2_jll with a git-tree-hash1
-        # which simulates an old manifest where LibGit2_jll was not a stdlib
-        badmanifest_test_dir2 = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps2")
-        @test success(addenv(
-            `$(Base.julia_cmd()) --project=$badmanifest_test_dir2 --startup-file=no -e 'using LibGit2'`,
-            "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
-        ))
-    end
 end
 
 @testset "code coverage disabled during precompilation" begin