Add H gate text to import for bell state docs/source/start.rst

[fieldofnodes]

Pre-Report Checklist

• [X] I am running the latest versions of pyQuil and the Forest SDK
• [X] I checked to make sure that this bug has not already been reported

Issue Description

In the docs, the line "Next, let’s construct our Bell State." followed by the code block

# construct a Bell State program
p = Program(
    Declare("ro", "BIT", 2),
    H(0),
    CNOT(0, 1),
    MEASURE(0, ("ro", 0)),
    MEASURE(1, ("ro", 1)),
).wrap_in_numshots_loop(10)

will generate an error if the use only uses the above import instructions

from pyquil import get_qc, Program
from pyquil.gates import CNOT, Z, MEASURE
from pyquil.api import local_forest_runtime
from pyquil.quilbase import Declare

There is no mention of the H gate.

If useful, provide a numbered list of the steps that result in the error.

Otherwise, just fill out the "Code Snippet" and "Error Output" sections below.

Code Snippet

Include a snippet of the pyQuil code that produces the error here.

Error Output

Additionally, please copy and paste the output of the above code here.

Environment Context

Operating System:

Python Version (python -V):

Quilc Version (quilc --version):

QVM Version (qvm --version):

Python Environment Details (pip freeze or conda list):

Copy and paste the output of `pip freeze` or `conda list` here.