3D Subplot with 2D subplots has messed up layout (3D plot appears in the center)

**Describe the bug**

When I make subplots with a 3D plot, it becomes centralized in the collated output.
```
a = plot(rand(10))

b = plot(rand(10))

c = plot(rand(10))

d =plot(rand(10), rand(10), rand(10))

plot(a, b, c, d)
```

**Version info**

Please provide the following:

1. output of julia command `versioninfo()`
```
Julia Version 1.4.0
Commit b8e9a9ecc6 (2020-03-21 16:36 UTC)
Platform Info:
OS: Windows (x86_64-w64-mingw32)
CPU: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-8.0.1 (ORCJIT, broadwell)
```

2. Output running the following in Julia 0.7 or greater: `using Pkg; pkg"status"` (if you are on Julia 0.6 or earlier run `Pkg.status()`)
``` [c52e3926] Atom v0.12.10
[94b1ba4f] AxisKeys v0.1.2
[5ae59095] Colors v0.12.0
[8f4d0f93] Conda v1.4.1
[717857b8] DSP v0.6.4
[31c24e10] Distributions v0.23.2
[ccffbfc1] EDF v0.1.2
[7a1cc6ca] FFTW v1.2.0
[28b8d3ca] GR v0.48.0
[6a3955dd] ImageFiltering v0.6.11
[e5e0dc1b] Juno v0.8.1
[23992714] MAT v0.7.0
[442fdcdd] Measures v0.3.1
[356022a1] NamedDims v0.2.21
[47be7bcc] ORCA v0.3.1
[5fb14364] OhMyREPL v0.5.5
[f0f68f2c] PlotlyJS v0.13.1
[91a5bcdd] Plots v1.0.11
[438e738f] PyCall v1.91.4
[295af30f] Revise v2.6.1
[f3b207a7] StatsPlots v0.14.5
[44d3d7a6] Weave v0.9.4
[10745b16] Statistics
```